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Does “Shared Nothing” Migration Mean the Death of the SAN?

November 30th, 2012 | Posted by Sid Herron in Best Practices | Hyper-V | Microsoft | Virtualization - (0 Comments)

You’ve probably heard that Hyper-V in Windows Server 2012 supports what Microsoft is calling “Shared Nothing” live migration. You can see a demo of that here, in a video that was posted on a TechNet blog back in July:

Now don’t get me wrong – the ability to live migrate a running VM from one virtualization host to another across the network with no shared storage behind it is pretty cool. But if you read through the blog post, you’ll also see that it took 8 minutes and 40 seconds to migrate a 16 Gb VM. (And I don’t know about you, but many of our customers have VMs that are substantially larger than that!) On the other hand, it took only 11 seconds to live migrate that same VM running on the same hardware when it was in a cluster with shared storage.

So I will submit that the answer to the question posed in the title of this post is “No” – clearly, having shared storage behind your virtualization hosts brings a level of resilience and agility far beyond what Shared Nothing migration brings. Still, for an SMB that has a small virtualization infrastructure with only two or three hosts and no shared storage, it’s a significant improvement over what they’ve historically had to go through to move a VM from one host to another: That has typically meant shutting the VM down, then exporting it to a storage repository that can be accessed by the other host (e.g., an external USB or network-attached hard drive), then importing it into the other host’s local storage, then booting it up…that can easily take an hour or more, during which time the VM is shut down and unavailable.

So Shared Nothing migration is pretty cool, but, as Rob Waggoner writes in the TechNet post linked above, don’t throw your SANs out just yet.

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Some Straight Talk about VDI-in-a-Box

April 4th, 2012 | Posted by Sid Herron in Citrix | VDI | VDI-in-a-Box - (9 Comments)

There is a lot of buzz about Citrix VDI-in-a-Box (“ViaB”), and rightly so: it’s a great product, and much simpler to install and easier to scale than a full-blown XenDesktop deployment. You don’t need a SAN, you don’t need special broker servers, you don’t need a separate license server or a SQL Server to hold configuration data. Unfortunately, some of the buzz – particularly some of the cost comparisons you see that show a $3,000 – $4,000 server for 30 or more virtual desktops, is misleading. So let’s talk seriously about the right way to deploy ViaB. For this exercise, I’m going to assume we need 50 virtual desktops. Once we’ve worked through this, you should be able to duplicate the exercise for any number you want.

First of all, I’m going to assume that we are building a system that will support Windows 7 virtual desktops – because I can’t see any valid reason why someone would invest in a virtual desktop infrastructure that couldn’t support Windows 7. There are two important data points that follow from this: (1) We should allow at least 1.5 Gb per virtual PC, and preferably 2 Gb per virtual PC. (2) We should design for an average of about 15 IOPS per Windows 7 virtual PC, because, depending on the user, a Windows 7 desktop will generate 10 – 20 IOPS. Let’s tackle the IOPS issue first.

Thanks to Dan Feller of Citrix, we know how to calculate the “functional IOPS” of a given disk subsystem. Here are the significant factors that go into that formula:

  • A desktop Operating System – unlike a server Operating System – has a read/write ratio of roughly 80% writes and 20% reads.
  • A 15K SAS drive will support approximately 175 IOPS. The total “raw IOPS” of a disk array built from 15K SAS drives is simply 175 x the number of drives in the array.
  • A RAID 10 array, which probably offers the best balance of performance and reliability, has a “write penalty” of 2.

With that in mind, the formula is:

Functional IOPS=((Total Raw IOPS x Write %)/(RAID Penalty)) + (Total Raw IOPS x Read %)

If we put eight 15K SAS drives into a RAID 10 array, the formula becomes:

Raw IOPS = 175 x 8 = 1,400

Functional IOPS = ((1,400x.8)/2)+(1,400x.2) = 560 + 280 = 840

If we are assuming an average of 15 IOPS per Win7 virtual PC, this suggests that the array in question will support roughly 56 virtual PCs. So this array should be able to comfortably support our 50 Win7 virtual PCs, unless all 50 are assigned to power users.

That’s all well and good, but we haven’t talked yet about how much actual storage space this array needs. That depends on the size of our Win7 master image, how many different Win7 master images we’re going to be using, and whether we can use “linked clones” for VDI provisioning, in which case each virtual PC will consume an average of 15% of the size of the master, or whether we’re permanently assigning desktops to users, in which case each virtual PC will consume 100% of the size of the master. For the sake of this exercise, let’s assume we’re using linked clones, and that we have three different master images, each of which is 20 Gb in size. According to the Citrix best practice, we need to reserve 120 Gb for our master images (2 x master image size x number of master images). We then need to reserve 3 Gb per virtual PC (15% of 20 Gb), which totals another 150 Gb. The ViaB virtual appliance will require 70 Gb. We also need room for the hypervisor itself (unless we’re provisioning another set of disks just for that) and for swap file, transient activity, etc., so let’s throw in another 150 Gb. That’s 490 Gb minimum. So we need to use, at a minimum, 146 Gb drives in our array, which would give us 584 Gb in our RAID 10 array.

How about RAM? If we allow 1.5 Gb per Win7 desktop, then 50 virtual desktops will consume 75 Gb. We need at least 1 Gb for the ViaB appliance, at least 1 Gb for the hypervisor, plus some overhead for server operations, so let’s just call it 96 Gb.

We can handle 6 to 10 virtual desktops per CPU core – more if the cores are hyper-threaded – so we’re probably OK with a dual-proc, quad-core server.

Now, I don’t know about you, but if I’m going to put 50 users onto a single server, I’m going to want some redundancy. I will at least want hot-plug redundant power supplies, and hot-plug disk drives. Ideally, I would provision “N+1″ redundancy, i.e., I would have one more server in my ViaB array than I need to support my users. I’m also going to want a remote access card, and probably an uplift on the manufacturer’s Warranty so if it breaks, the manufacturer will come on site and fix it.

By now, you’ve probably figured out that we are not talking about a $4,000 server here. I priced out a Dell R710 – using their public-facing configuration and quoting tool – with the following configuration, and it came out to roughly $11,000:

  • Two Intel E5640 quad-core, hyper-threaded processors, 2.66 GHz
  • 96 Gb RAM
  • Eight 146 Gb, 15K SAS drives
  • PERC H700 controller with 512 Mb cache
  • Redundant hot-plug power supplies
  • iDRAC Enterprise remote access card
  • Warranty uplift to 3-year, 24×7, 4-hour response, on-site Warranty

(NOTE: This is a point-in-time price, and hardware prices are subject to change at any time.)

The ViaB licenses themselves will cost you $195 each. Be careful of the comparisons that show the price as $160 each. ViaB is unique among Citrix products in that the base cost of the license does not include the first year of Subscription Advantage – yet the purchase of that first year is required (although you don’t necessarily have to renew it in future years). That adds $35 each to the cost of the licenses.

Finally, If you don’t have Microsoft Software Assurance on your PC desktops – and my experience is that most SMBs do not – you need to factor in the Microsoft Virtual Desktop Access (VDA) license for every user. This license is only available as an annual subscription, and will cost you approximately $100/year.

So, your up-front acquisition cost for the system we’ve been discussing looks like this:

  • Dell R710 server – $11,000
  • 50 ViaB licenses @ $195 – $9,750
  • 50 Microsoft VDA licenses @ $100 – $5,000

Total aquisition cost: $25,750, or $515/user. Not bad.

But wait – if we’re going to compare this to the cost of buying new PC, shouldn’t we look at the cost of ViaB over the same period of time that we would expect that new PC to last? If we assume, like many companies do, that a PC has a useful life of about 3 years, then we should actually factor in another two years of VDA licenses, and two years of Subscription Advantage renewal for the ViaB licenses. That pushes the 3-year cost of the ViaB licenses to $13,250, and the cost of the VDA licenses to $15,000. So the total 3-year cost of our solution is $39,250, or $785/user.

If you want N+1 redundancy, you’re going to need to buy a second server. That would push the cost to $50,250, or $1,005/user.

What conclusions can we draw from all this? Well, first, that VDI-in-a-Box is not going to be significantly less expensive than buying new PCs, if you actually do it right. However, it is competitive with the price of new PCs, which is worth noting. As long as the price is comparable, which it is, we can then start talking about the business advantages of VDI, such as being able to remotely access your virtual desktop from anywhere, with just about any device, including iPad and Android tablets, and about the ongoing management advantages of having a single point of control over multiple desktops.

Also, as you scale up the environment, the incremental cost of that extra server that’s required for N+1 redundancy gets spread over more and more users, and becomes less significant. For example, if we’re building an infrastructure that will support 150 virtual desktops, we would need four servers. Total 3-year cost: $128,750, or $858.33/user for a robust, highly redundant virtual desktop infrastructure. In my opinion, that’s a pretty compelling price point, and you won’t be able to hit that price point with a 150-user XenDesktop deployment, because of the other server and storage infrastructure components that you need to build a complete solution. On the other hand, XenDesktop does include more functionality, like the rights to use XenApp for virtual application delivery, ability to stream a desktop OS to a blade PC or a desktop PC, rights to use XenClient for client-side virtualization, etc.

But if all you want is a VDI solution, ViaB is, in my opinion, the obvious choice. It’s clear that Citrix wants to position VDI-in-a-Box as the preferred VDI solution for SMBs, meaning anyone with 250 or fewer users…and there’s no reason why ViaB can’t scale much larger than that.

For more information on ViaB, check out this video from Citrix TV, then head on over to the Citrix TV site to view the entire ViaB series…

**** EDIT April 12, 2012 ****
You may already be aware of this, but Dell has announced a ViaB appliance that comes pre-configured, with both XenServer and the ViaB virtual appliance already installed. Oddly enough, even though Moose Logic is a Dell partner, I couldn’t get Dell to tell me what one would cost. Their answer was that I should call back when I had a specific customer need, and they would work up a specific configuration and quote it. I considered calling back with a fictitious customer requirement, but decided that I didn’t want to know badly enough to play that game.

They did, however, tell me what the basic server configuration was – and it was very close to the configuration I’ve outlined above: two X5675 processors, 96 Gb of RAM, eight 146 Gb drives in a RAID 10 array, Perc H700 array controller (don’t know how much cache, though), and iDRAC Enterprise remote access card. I do not know whether it has redundant power supplies (although I would certainly hope so), nor exactly what Warranty is included…perhaps that option is left up to the customer.

That gave me at least enough information to run a sanity check on the configuration. The array would provide 960 functional IOPS, which should be adequate for an 80 user system – which is how the appliance is advertised – depending, of course, on the percentage of power users. Also, the array should provide enough storage to handle the needs of most SMBs, unless they have an unusually large number of images to maintain.

One of my Citrix contacts recently told me that the Dell appliance was priced at $440/desktop for an 80 concurrent user configuration, which is very much in line with the cost per user in the post above, considering that $100 of my $515/user number was for the first year of Microsoft VDA licenses, which, to my knowledge, are not included with the Dell appliance.

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SAN Tips – Storage Repository Design

July 26th, 2010 | Posted by Shane Kalles in Best Practices | Education | Snapshotting | Storage | Virtualization - (0 Comments)

Back with another Moose Logic video for your viewing pleasure. In this installment, our own Steve Parlee, Moose Logic’s Director of Engineering, talks about SAN storage repository design concepts, and the effects your design choices have on things like snapshots, disk usage, and overall performance. In the process, you’ll also learn what we consider to be “best practice,” and some of the reasons why. As always, your comments will be appreciated. Enjoy!

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Just Sign the Check Right Here – We’ll Fill In the Amount Later

July 20th, 2010 | Posted by Sid Herron in Citrix | Licensing | Microsoft | Virtualization | VMware | XenServer - (0 Comments)

Back in the old days of minicomputers and mainframes, we used to joke about IBM’s ability to, for all intents and purposes, get the customer to sign a blank check. They were better than anybody I’ve ever seen at getting people to commit to a solution when they really had no idea what the ultimate cost would be – and they were successful because of another cliche (which became a cliche because it was so accurate): “Nobody ever got fired for buying from IBM.” The message was basically, “Yes, we may be more expensive than everybody else, but we’ll take care of you.”

For the most part, those days are long gone, which made it all the more amazing to me to read that VMware is adopting per-VM licensing for most of its management products.

The article nails the basic problem with this licensing approach:

You know how many processors you have on a system, and that’s a fixed number. But the number of VMs on one host — let alone throughout your entire infrastructure — is regularly in flux. How do you plan your purchasing around that? And how do you make sure you don’t violate your licensing terms?

Hey, it’s easy – you just let VMware tell you what to put on your check at the end of the year:

You estimate your needs for the next year and buy licenses to meet those needs. Over the course of those 12 months, vCenter Server calculates the average number of concurrently powered-on VMs running the software. And if you end up needing more licenses to cover what you used, you just reconcile with VMware at the end of the year.

And, before you ask, no, you don’t get money back if you use fewer licenses than you originally purchased.

Sounds to me like a sweet deal – for VMware.

By comparison, the most expensive version of XenServer is $5,000 per server (not per processor, not per VM), and all of the management functionality is included. And the basic version of XenServer, which includes live motion, is free, and still includes the XenCenter distributed management software. (Here’s a helpful comparison chart of which features are included in which version of XenServer.)

A number of years ago, I attended a seminar that discussed the product adoption curve, and how products moved from the “innovation” phase to the “commodity” phase. The inflection point for a particular market was referred to as the “point of most” – where most of the products met most of the needs of most of the customers most of the time. When this point is reached, additional feature innovation no longer justifies a premium price.

The fact is that XenServer and Hyper-V are rapidly achieving feature parity with VMware. If we haven’t reached the “point of most” yet, we certainly will before much more time goes by. So even if you have a substantial investment in VMware already, at some point you have to re-examine what it’s costing every year, don’t you? Or are you OK with just signing a check and letting them fill in the amount later?

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Citrix Branch Repeater VPX Licensing Tutorial

April 29th, 2010 | Posted by Steve Parlee in Branch Repeater | Citrix | Licensing - (1 Comments)

I recently implemented both the new Citrix Access Gateway (CAG) VPX and the Branch Repeater VPX within our development lab. Both are “virtual appliances” designed to run directly on a XenServer host. Both are impressive products and work great – in fact, we can use “live motion” to move the CAG between XenServers while running video in a XenDesktop session with not even a pause in the video playback. The CAG moves with no interruption in service. NONE!

But this isn’t just a post to sing the praises of the virtual appliances. Rather, it’s about LICENSING!!! Specifically, licensing the Branch Repeater VPX.

As with many Citrix products, obtaining the license and getting it properly installed is not necessarily easy and intuitive…and in many cases (particularly with new products), we’ve found that the Citrix licensing support team does not know all the ins and outs of licensing a specific product either. That is not intended as a slam on this team. They do the best they can – but Citrix is a big company now, and sometimes it takes a while for information on new products to filter down to the front-line troops. In this case they worked with me for quite some time until we got this figured out (so there is at least one guy on the Citrix support team who now knows how this works).

So…now that I’ve gone through the pain, I thought I’d try to spare you from it if I can. (You’re welcome.)

One complication you’ll encounter is that, depending upon what you’re attempting to accomplish, these appliances may require one license or two. For example, with the CAG, if you are only going to use it for running secured sessions to a web interface (the equivalent of the legacy Citrix Secure Gateway) then you only need a “platform license.” However, if you also plan to run SSL VPN sessions though the CAG, you will need Access Gateway Universal licenses for your users, which will be rolled into a second license file.

Access Gateway licensing isn’t new and it’s pretty well understood. But what about the Branch Repeater? Just as with the CAG, the Branch Repeater may require one license or two, depending upon the functionality you need. If you are going to use the Branch Repeater VPX to connect to another (physical or virtual) Branch Repeater then you only need a platform license. However, if you want to take advantage of its ability to support client PCs that use the Branch Repeater Plug-in, you will need a second license to enable that feature. So we finally come to the topic of this post: how do you get the license file(s) onto your new Branch Repeater VPX?

First, you must log onto the “MyCitrix” web site with your account credentials, and access the Licensing Tool Box to activate and allocate the license. That part of the process is well documented, and if you’re a Citrix customer, you’ve probably done it at least once. The tricky part is what you have to do to download the VPX license file, what you need to enter in the Repeater itself, where to put it, and what you should see.

Here’s what we learned (NOTE: Click on any graphic to view full-sized):

  1. On the Branch Repeater VPX Web-based management interface, access the “Manage Licenses” screen, and in the right panel, choose “local” as shown below, and click the “Apply” button.
    License Server Configuration

    License Server Configuration

  2. Then click on the “License Information” tab and you will see something similar to this next image. What you will need from this screen is the “Local License Server Host Id:” Write down this information – you will need it in the next step.
    Information Used for License Management

    Information Used for License Management

  3. Now you can download the license file from your “MyCitrix” portal. Save it to your PC, and make a note of where you saved it. As part of the process of downloading the license, you must enter the license server ID. Traditionally, you would enter the name of the Citrix license server in this field (and it was case-sensitive, which tripped up a lot of users). But in this case, the system is expecting the MAC address of the Branch Repeater VPX itself…which is what you just copied in Step 2. Another difference is that in the past the License Server Host Type was always set to “HostName.” However, there is now a drop down box with a second choice, “ETHERNET.” For the Branch Repeater VPX, you want to select “ETHERNET,” and then enter the host id that you wrote down in Step 2:
    Downloading the License File from MyCitrix

    Downloading the License File from MyCitrix


    In case you’re wondering, the MAC address we’re using is the address of the first interface on the Branch Repeater VPX, as displayed in XenCenter. If you want to find it in XenCenter click on the VM in the left column and then select the Network tab in the right window and you should see it there:
    XenCenter Display

    XenCenter Display

  4. Now that you have your license downloaded to your local PC, you need to add it to your Branch Repeater. Access the “Local Licenses” tab and click the Add button (note that you will not see all the content in the window as shown here until you’ve added your license):
    Local Licenses Display

    Local Licenses Display


    After you click Add, this screen will appear and you will need to browse to the location where you saved your license file, and click the “Install” button:
    Add License

    Add License


    Now the “Local Licenses” tab should be populated with content:
    Local Licenses Display

    Local Licenses Display


    Next, go to the “Licensed Features” tab. You should see your features listed as shown below:
    Licensed Features

    Licensed Features

  5. As mentioned earlier, if you plan to support client PCs that have the Branch Repeater Plug-in, you will need another license to enable this feature. Once again you will need to go to your MyCitrix portal and follow the same procedure as you did for your platform license to obtain the Plug-in license. Once you have the Plug-in license you will need to add it to the Virtual Appliance in the same manner as you added the platform license. Once that’s done, if you click the down arrow under “Local Licenses” you will see both licenses:
    Manage Licenses Screen

    Manage Licenses Screen


    Finally, if you click the “Licensed Features” tab, both licenses should show up with the number of licenses available:
    Licensed Features

    Licensed Features

This should be all you need to get the Branch Repeater VPX licensed. Now you just need to get it configured correctly… but that’s another blog post.

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XenServer Host Is In Emergency Mode

April 15th, 2010 | Posted by Steve Parlee in Citrix | Troubleshooting and How-Tos | Virtualization | XenServer - (8 Comments)

It’s 8 pm on a Sunday evening, and I get a panicked call from a customer because he cannot connect to his XenServersTM via the XenCenterTM management tool. However, as near as he could tell, all of the hosted virtual machines were up and running and in a healthy state. He had unsuccessfully tried to point the XenCenter management tool at another member of the XenServer pool but was unsuccessful.

So what happened and how do you fix it?

This situation can happen for several reasons but generally it happens when there are only two servers in the XenServer pool, and the pool master suddenly fails. In essence, what happens is the surviving server (let’s just call it the “slave”) can no longer see its peer, the pool master, so it assumes it has been stranded and goes into emergency mode to protect its own VMs. There are other ways this can happen (an incorrectly configured pool with HA turned on for example), but this is the most common reason that I have personally experienced.

Depending upon the situation, you may not be able to ping the master server because it is actually down, or you may be able to ping the server but it is in an inconsistent, “locked up”, state such that it cannot answer requests to it. If you are able to connect to the console of the master server either directly with a monitor, keyboard, and mouse (the old fashioned way) or through a remote management interface (DRAC, ILO, ILOM, etc) the server may appear to be running, but you may not be able to do anything with it.

At this point you may be thinking, “This is no big deal – just reboot the machine and it will be fine.” If you are lucky that may actually solve the problem, but in many cases it will not. What you might see is that after the master reboots you will be able to connect to the master but you will not see the slave. Or it may be that your master is truly broken and you are not able to simply reboot it due to a system or hardware failure. But, of course, you’ve still got to get your pool online and working again regardless.

During this period of time, if you try to use a tool such as Putty to connect to the slave via its management interface, you may not be able to connect to it either. If you try to ping the slave on the management interface you may not get any replies. But if you connect to the console of the slave (again, either the physical console or via a remote management interface) you will probably see that the machine is running, but if you look at XSconsole it will appear that the management interface is gone because there will be no IP address showing. By now you’ll probably be scratching your head because the strange thing is all the VMs are running.

So at this point your master appears to be down, or at least impaired, you’ve got no management interface on the slave, your pool is broken and you cannot manage the VMs. So what do you do?

Well, if this happens to you and your VMs are still up and running the first thing you should do is take a deep breath, because more than likely it is not as bad as you might think. XenServer is a robust platform and if the infrastructure is built correctly (and I’m going to quote a customer), “you can really slam the things around and they still work”.

After you take a deep breath and let it out slowly, from the console of the slave server, you will need to access the command line and start by typing:

xe host-is-in-emergency-mode

If the server returns an answer of “True” then you’ve confirmed that the server has gone into emergency mode in order to protect itself and the VMs running on it. (If the server returns an answer of “False” then you can stop reading, because the rest of this post isn’t going to help you.)

Assuming you receive the answer of “True” the slave server is in emergency mode because it cannot see a master – either because the master is actually down, or because the management interface(s) is(are) not working. Therefore, the next step is to promote the slave to master to get it out of emergency mode. We do this by typing:

xe pool-emergency-transition-to-master

At this point the slave server should take over as the pool master and the management interface should be available again. Now if you type the xe host-is-in-emergency-mode command again you should get an answer of “False”.

Now, open XenCenter again. It will first try to connect to the server that was the master, but after it times out it will then attempt to connect to the new master server. Be patient, because eventually it will connect (it may take several seconds) and you will again see your pool and be able to manage your VM’s. If some of the VMs are down because they were on the server that failed you’ll be able to start them on the remaining server (assuming you have shared backend storage and sufficient processor and memory resources).

Now what about the master if it has totally failed? What do I do after I’ve fixed, say, a hardware problem in order to return it to my pool?

If the following two conditions are true:

  1. You are using shared storage so that your VMs are not stored on the XenServer local drives, and
  2. You have built your XenServers with HBAs (fiber or iSCSI) rather than using Open iSCSI, which means the connectivity information to your backend SAN will be stored within the HBA,

…then it may be much simpler and quicker just to reload the XenServer operating system. (If you do not have shared backend storage, which means your VMs are on local storage, DO NOT DO THIS). I can rebuild my XenServers from scratch in about 20 – 30 minutes and have them back in the pool and running.

If either of those two conditions is not true then, depending upon your situation, recovery may be significantly more difficult. It could be as simple as resetting your Open iSCSI settings and connecting back to your SAN (still easy but takes more time to accomplish) or it could be as painful as rebuilding your VMs because you lost your server drives. (OUCH!)

Real world example: I recently had a NIC fail on the motherboard of my master server. Of course since the NIC was on the motherboard it meant the whole motherboard had to be replaced which significantly modified the hardware configuration for that server.

In this case, when I brought that XenServer back online it still had all the information about the old NICs showing in XenCenter, plus it had all the new NICs from the new hardware. Yes I could have used some PIF forget commands to remove the NICs that no longer existed and reconfigure everything but that would have taken me a bit of time to straighten out. Since I had iSCSI HBAs attached to a Datacore SAN (great product, by the way) for shared storage, all I did was reload XenServer on that machine, modify the multipath-enabled.conf file (that is a different blog topic for another day), and rejoin the server to the pool. Because the HBAs already had all the iSCSI information saved in the card, the storage automatically reconnected all the LUNs, the network interfaces took the configuration of the pool, and I was back online and running in less than 30 minutes.

After you repair the machine that failed and get it back online, you may want it to once again be the master server. To do this type:

xe host-list

You will get a list of available servers with their UUID’s. Record the UUID of the server that you want to designate as the new master and then type:

xe pool-designate-new-master host-uuid=[the uuid of the host you want]

After you type this your pool will again disappear from XenCenter, but after about 20 – 30 seconds (be patient) it will reappear with the new server as the master. Your pool should now be healthy, and you should again be able to manage servers as normal.

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Understanding Microsoft Server Virtualization Rights

February 9th, 2010 | Posted by Sid Herron in Licensing | Microsoft | Virtualization - (0 Comments)

So, grasshopper, you have decided to take the plunge and virtualize your server infrastructure. Someone (perhaps us) explained the business benefits of virtualization, you decided that it made sense, and that it’s time to make the move. But do you know how virtualization will affect your Windows Server licensing model?

The first thing you need to know is that Windows Server licenses are assigned to physical hardware, not to server workloads. When you purchase a license, you must “assign” that license to a physical server. How do you do that? Well, in today’s world, there is no formal process for doing that, although if it makes you feel better, you can write it down somewhere.

You may assign more than one license to a physical server, but you may not assign the same license to more than one physical server. You may reassign a license from one physical server to another, but not more frequently than every 90 days, unless the server it was assigned to is being retired due to “permanent hardware failure.”

Sound reasonable so far? Of course it does. Right up until the license model runs head-on into one of the coolest features of virtualization: live motion. Most virtualization platforms, including Microsoft’s Hyper-V R2, allow you to easily move a virtual server from one physical host to another. Great feature, right? But if you do it, you may have just violated your Windows license agreement.

I say “may” because different versions of Windows Server come with different virtualization rights. For example, a Windows Server Standard license can be used to run one physical instance of Windows (and by “physical instance,” I mean Windows is installed directly on the hardware) or one virtual instance of Windows, but not both – unless the physical instance is being used solely to manage the virtual environment.

Let me say that another way: If you buy a single license for Windows Server Standard Edition with Hyper-V, you can install it directly on the hardware without bothering with the Hyper-V role. Or you can install the Hyper-V role, have one virtual Windows Server running on top of Hyper-V, and use the physical instance exclusively to manage the virtual instance. Of course, you haven’t really gained anything by doing that…but you can purchase additional copies of Windows Server Standard, assign them to the same physical host, and run more virtual servers on Hyper-V.

Thinking this scenario through, then, if you currently have a bunch of physical Windows Servers – each licensed with Windows Standard Edition – and you want to virtualize them all, that’s no problem. You can reassign your server licenses to your virtual hosts and be perfectly legal. As long as you don’t move a server from one host to another. But if all you own are Standard Edition licenses, and you move a server from one host to another, you’ve just violated the license agreement – unless you own a “spare” server license that you have “assigned” to the target server (the host you’re moving it to) but that is not being used.

Now, in the scenario I just described, it’s possible that the most cost-effective thing you could do is to just buy a few additional licenses as “spares” rather than re-licensing your entire environment. But let’s move ahead – once we’ve covered the other Windows editions that are available to you, you’ll be better able to decide what makes financial sense for your project.

Windows Server Enterprise Edition comes with expanded virtualization rights. Each Enterprise Edition license gives you the rights to run one physical instance and up to four virtual instances on the physical host to which it is assigned. Once again, if you want to run all four virtual instances, then the physical instance may only be used to manage the virtual environment. If you want to run other services on the physical instance – and that’s actually fairly common in a Hyper-V deployment – then you only get to run three virtual instances. And you may not split the license across multiple physical hosts.

The “estimated retail price” (just the license, no Software Assurance, assuming Open Business pricing) for Windows Enterprise is $2,358, vs. $726 for Windows Standard. So Enterprise is less expensive than four copies of Standard. Therefore, if you need to buy new licenses (perhaps you’re upgrading from Server 2003 to Server 2008 as part of your virtualization project), it may make sense in a small environment to buy a copy of Enterprise Edition for each virtual host, and perhaps supplement it with a few spare copies of Standard Edition. Here’s an example:

Let’s say you have a total of nine physical servers today, and you want to virtualize them on three dual-processor virtualization hosts. (You could probably run them on two hosts, but if one failed, it might be a stretch to run all nine on one host. If you start with three hosts, and one fails, you still have two to carry the load.) You could buy nine new copies of Windows Standard Edition for $6,534, but you’d have no flexibility to use live motion to move things around. On the other hand, you could buy three copies of Enterprise Edition for your three hosts for $7,074, and effectively have one “spare” instance on each host that’s available for moving a virtual machine from one host to another.

Of course, that may not be quite enough if you want to completely unload one of your servers (perhaps to take it off-line for maintenance), because unless you’re prepared to shut down one VM completely, you’re going to need to run five VMs on one of your remaining servers. Since you may not know in advance which server needs to assume the extra VM workload, you could just buy three additional copies of Standard Edition, and assign one to each host. That would push your total license acquisition cost to $9,252, but you would then be licensed for five VMs on each of your hosts.

The ultimate in flexibility is Windows Server Datacenter Edition. Datacenter Edition is licensed per processor socket rather than per physical host, but includes unlimited virtualization rights. You can run as many VMs on your hosts as they’re capable of running, and move them around to your heart’s content. If you just don’t want to worry about what’s running where or whether or not it’s technically legal to move a given VM around, this is the license model to use.

Of course, this is also the most expensive edition of Windows. The estimated retail price for Datacenter Edition is $2,405 per processor socket (regardless of the number of cores per processor). So it would cost $14,430 to license three dual-processor servers with Datacenter Edition. This probably isn’t cost effective if you’re only virtualizing nine servers. However, if you have lots of servers, and many of them are fairly lightly loaded (in terms of processor utilization), the picture could change. If your average consolidation ratio is greater than or equal to four servers per physical processor then Datacenter Edition becomes the most cost-effective license.

In fact, if you’re even close to that 4:1 ratio, you should strongly consider Datacenter Edition, for two reasons:

  1. Windows environments inevitably grow. However many servers you have today, you’re probably going to have more of them a year from now. With Datacenter Edition, you can continue to fire up new servers to the limits of your hardware without having to buy more server licenses.
  2. AMD already has six-core processors. You know the “arms race” between Intel and AMD will continue. So the number of servers per processor that you can reasonably expect to support will continue to increase as the processors themselves become more powerful and contain more cores, and as this happens, Datacenter Edition will look better and better.

Note that everything we’ve discussed holds true if you’re virtualizing on XenServer or VMware rather than on Hyper-V. The only difference is that you won’t be using any of the allowed physical instances of Windows.

If you want to delve deeper into this issue, you can download a copy of the Microsoft Product Use Rights document from their Web site. Happy virtualizing!

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What is Virtualization?

December 4th, 2009 | Posted by Shane Kalles in Computer Basics | General | Virtualization - (0 Comments)

Virtualization can mean different things depending on who you ask so we are going to take a broad look at what virtualization is, the different forms it comes in, and why it is so popular.

This is going to be pretty basic stuff so if you are looking for more advanced material I promise we will have advanced stuff in future posts.

Virtualization has been getting a lot of buzz the last few years as it moved from being “bleeding edge” technology to becoming an industry standard. You may have even heard that there are lots of benefits to virtualizing your datacenter…but you may not be sure whether it’s for you, how it works, or even what it means.

There are several kinds of virtualization, including server virtualization, storage virtualization, application virtualization, network virtualization, and desktop virtualization. But when most folks talk about virtualization, they’re referring to server virtualization, so that’s what we will cover today.

So, what is server virtualization?  Simply put server virtualization is the technology that is designed to allow multiple (virtual) servers to reside on a single piece of (physical) hardware and share the resources of the physical server – while still maintaining separate operating environments, so that a problem that crops up in one virtual server won’t affect the operation of others that may be running on the same physical “host.” To help explain what this means I’m going to use the house and condo analogy.

Let’s say you’re a land developer and you build residential property. You cut your land into smaller plots and build one house per plot. As part of the land development, you need to bring in all the utilities from the main street to each and every plot. All of this development costs money.  To make matter worse you know that your city’s population is growing, you’re running out of land to build on, and you also need to control the spiraling costs of building materials. How do you cut cost and provide more homes for a growing population on a limited amount of land?

Figure 1 - Typical cul-de-sac USA

Figure 1 - Typical cul-de-sac USA

Perhaps instead of building single-family homes and having one resident per plot you start building condominiums that hold several residents each. Now the utilities that are brought in to the condo complex are shared by all the residents and yet no one ever sees the other residents’ bills. You’re making more efficient use of the land you have and not wasting time and money bringing in utilities to each individual house. Plus one yard is easier to take care of than ten yards.

1 & 2bd Condos Available Now!!

Figure 2 - 1 & 2bd Condos Available Now!!

So how does this relate to server virtualization?

Each plot of land is a physical server, the structure you build on that plot is a server “workload” (i.e., Exchange, SQL, file server, print server, etc.), and the city is your data center. The utilities are things like power, cooling, and network connectivity. When there is only one workload per physical server, a lot of space and resources get wasted. It’s common to see only 10-15% (if that) processor utilization on physical servers which run only one operating system and one application.

With server virtualization we can now create several “virtual” servers on one physical piece of hardware – think of the hardware as little “server condos” if you like. Just as you can have one-bedroom, two-bedroom, and three-bedroom units in a single building, you can allocate differing amounts of processing and memory resources to the virtual servers depending on the requirements of each individual workload. Each virtual server can now share the physical resources of the host machine with the other virtual servers and never know that they are sharing. In fact, each virtual server “thinks” it’s running on its own dedicated hardware platform. By doing this you can now utilize 80-90% of the processing power of the hardware you own, and cut down on the total amount of power, cooling, and floor space you need in your data center.

For example (just pulling numbers out of the air), let’s say that you’ve been paying an average of $5K each for servers that would handle a single workload. If you need four of them, that’s $20K in hardware cost. But if you can buy one server for $8 – 10K to virtualize these 4 machines, that’s a significant reduction in hardware cost. And with fewer machines to plug in and keep cool, your savings can be up to 40% on power consumption alone. (Did you know that we’ve now reached the point where, over the service life of a typical new server, it’s going to cost you more to keep it cool than it cost you to buy it?)

Since the virtual servers are all located on one physical box you now have fewer pieces of hardware to maintain – allowing the IT staff to use their time more efficiently. You’ll save space in your data center. You’ll also cut down on the amount of waste (some of it hazardous) that must be recycled or disposed of when your hardware finally reaches its end-of-life.

You’ve also cut down time needed to bring a new server on line. In the past you would have had to acquire the hardware, assemble it, rack it, connect it to the network, install and patch the OS, install and configure the application, test it all, and finally put it into service. Now that the servers are virtual they can be created, configured, and put into production in a few hours as opposed to the weeks it used to take. In some cases, by using templates for commonly-needed workloads, it can take only minutes. This makes for a much more flexible and scalable environment.

So server virtualization can:

  • Cut hardware costs
  • Cut energy costs (for both power and cooling)
  • Cut system maintenance time and costs
  • Create a very scalable and flexible data center
  • Save space
  • Create a more environmentally friendly data center (a.k.a. “green computing”)

These are the main reasons that server virtualization has become an industry standard. According to folks like Gartner, we’ve now reached the point where the majority of new servers placed into service are being virtualized, and the majority of enterprises have made it a standard practice to virtualize all new servers unless there is a compelling reason why a server can’t or shouldn’t be virtualized. Virtualization also makes it easier to implement things like high availability, disaster recovery, and business continuity, but that’s a subject for a future post.

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Installing Server 2008 R2 on XenServer 5.0

December 3rd, 2009 | Posted by Jeromy Carman in Citrix | Microsoft | Virtualization | XenServer - (2 Comments)

Recently I had my first opportunity to create a Windows 2008 R2 virtual machine on Citrix XenServer 5.0. When I attempted to install the operating system I ran into an interesting issue where the installation would hang right at the initial Windows install screen and the CPU usage pegged at 100%. Once that happened no matter how long I waited the installation never progressed beyond that point.

Of course what did I do? I turned to Google and quickly found the following article which provided a workaround for the issue I was having.

I followed the advice in the article and after running the “xe vm-param-set uuid= platform:viridian=false” command as outlined in the article was able to install Windows Server 2008 R2.

Two more things are worth mentioning here, which are not specifically addressed in the previously referenced article:

  1. With Windows 2008 R2 I was able to install the XenServer 5.0 tools with none of the problems others people are having with Windows 7 installations.
  2. This issue has been resolved in XenServer v5.5!

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Let the Reader Beware

November 18th, 2009 | Posted by Sid Herron in Citrix | High Availability | Virtualization | VMware - (0 Comments)

The TechTarget family of blog sites has a lot of great information. That’s why we have several of their sites linked in our Blogroll (under “Virtualization” in the right sidebar). But one thing that I don’t like about their sites is that – unlike this blog – there is no way to directly comment on their posts. That makes it difficult to respond to posts like the one last week on VMware’s High Availability (VMHA).

In that post, author David Davis opens by stating:

VMware’s High Availability (VMHA) provides high availability to any guest operating system at a potentially much lower cost than other HA options (as you don’t have to pay per virtual machines [VMs] or per server; VMHA is included in the price of vSphere).

I have a couple of problems with this statement.

First, I don’t know what “a potentially much lower cost” means. Is it less expensive than other HA options, or isn’t it? If it is, which other HA options are you comparing it to? If you’re going to throw that line out there, shouldn’t you give us the data on which the statement is based?

Second, it appears that the “lower cost” claim is primarily based on the fact that VMHA is included in the price of vSphere, rather than requiring a separate license. That’s a little like claiming that the high-end German sound system is less expensive if you get it in a Mercedes – because it’s standard equipment – whereas if you want one in your Malibu you have to buy it separately. What matters is the total amount of money I have to spend to get all the functionality I need, isn’t it?

It is true that with, say, Citrix XenServer, you have to purchase a Citrix Essentials for XenServer license to get HA functionality. That will cost you, at the suggested retail price (which nobody actually pays), $2,500 per XenServer for the Enterprise Edition. But the copy of XenServer you’re putting it on is free. On the other hand, vSphere 4 lists for $2,875 per processor, so if I’m using dual-processor servers, I’m looking at $5,750 for vSphere 4 compared to $2,500 for that copy of Essentials for XenServer. If I’m using quad-processor servers, vSphere 4 is going to run $11,500, but I still only need that single license for Essentials. And don’t forget the cost of VirtualCenter to control my vSphere environment, whereas XenCenter is, again, free, and runs on a workstation rather than requiring a dedicated server.

The point of this post is not to argue the relative merits of vSphere vs. XenServer, nor of whose HA feature is better. In fact, if you follow this blog, you’ll know that we’ve raised some red flags regarding how to properly deploy XenServer HA without risking potentially “career-altering” disasters. The point is simply that the old adage “don’t believe everything you read” is particularly appropriate for stuff you read on the Internet. (But you already knew that, right?)

People who throw out unsubstantiated generalized statements need to be challenged. If the TechTarget site allowed comments, I would have challenged the statement there. Since they don’t, I’m challenging it here. If I’m missing something, David Davis (or anyone else, for that matter) is welcome to comment on this post and point out what it is.

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