Citrix, Windows 2008, Windows 2008 R2, XenDesktop, , ,

If you’re used to check the IMA service and verify if everything is running fine on your XenDesktop 4 or XenApp environment, you won’t find any IMA in XenDesktop 5. This is one of the huge changes Citrix have done in the new XenDesktop, this is a major change because no more IMA means many things in term of architecture and product functionality.

So as I just mention, no IMA in XenDesktop 5 Controller (DDC), which means there is no IMA data store or local host cache (!!!) No more XML Blob, there is no more Active Directory Configuration Wizard or Farm OU, XenDesktop 5 doesn’t need Terminal Services any more, everything is stored in a brand new SQL database and there is no support for Oracle or Access. <– Wow ! These are a big changes right ?  I will explain more the impact of these change regarding what we’re used to and the consequences.

First thing first, when you want to install XenDesktop 5, you have choice between the “Quick Deploy”, “Join existing deployment”,  “Desktop deployment” and “Application deployment”. You can also notice the installer is simpler than the one in XenDesktop 4

  • “Quick deploy” option is the fastest way to deploy a fully functional XenDesktop installation. All in one box, Citrix License Server, the DDC, and Database.
  • “Join existing deployment” add a XenDesktop Controller to an existing site.
  • “Desktop deployment” advanced installation for large deployment, to use with Citrix Provisioning Services.

Regarding the installation, on the server side, XenDesktop Controller supports Windows Server 2008 and 2008 R2 only, exit Windows 2003.

If you want to use the “Quick Deploy” mode, then all components must be on same box, it also assumes SQL Express is installed on same machine. Microsoft PowerShell 2.0 is downloaded during the installation, you will need to manually install PowerShell 2.0 if you don’t have internet access. (more…)

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Stephane Thirion

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  • Hi,

    In the Citrix Database chart (http://support.citrix.com/article/CTX114501) only SQL 2008 (and not 2005 SP3 as mentioned in your article) is supported.

    The Machine Creation Service smells as ‘linked clone’ to me (and I prefer PVS). Quick Deploy is meant for quick PoC’s and might have customers wondering why a ‘real’ implementation takes so much more time (and is so much more expensive).

    All in all I really like the improvements (and your article) though…..

    Rene Lindeboom

  • Hi Rene,
    Indeed the databases requirement changed for the final release.
    Thx to point it out !

    Cheers,

    Stephane

  • Arjan Beijer

    Hi Stephane,

    In other documents SQL 2005 is mentioned. Also i already did a installation with a SQL 2005 server and it works fine.

    Also the integration with PVS is not optimal, as there is no wizard to automatically create PVS based computers. Needs improvement !

    Your article is great !

    regards,

    Arjan

  • Arjan Beijer

    @Rene

    It does look like linked clones, but it works differently. It uses the PVS technology to create a identity disk. So no sysprep like in linked clones !

  • @Arjan

    OK, the from ‘machine identity’ point of view I do agree with you – but looking at storage and version management I still prefer PVS as it gives you far more control without autocreating snapshot and difference disks on host storage…..

  • Disclaimer: I am a Citrix employee, but nothing written here should be taken as an official communication from Citrix.

    @Arjan: while SQL 2005 may have worked in your environment, it is not a supported platform. If you are using SQL 2005 and you have problems, it’s very likely the first thing any Citrix representatives will say will be to move to SQL 2008.

    One other general comment: MCS is not intended for POCs and small deployments only; it scales to large deployments as well, but we don’t yet have any reference architectures available to recommend to customers, so this is why you may see it being talked about being suitable for small scale only *at present*. Reference architectures are being worked on though.

  • @Philip; My first tests with MCS and pooled desktops showed one snapshot base disk being created on each selected storage repository (I have two SR’s in my testlab) and also two diff disks being created for a ‘pooled’ (or shared) desktop session (to be able to revert to the çlean diff disk?). At one moment on my xenserver host even more diff disks seemed to have been created (up to five or six for the same pooled desktop).

    It takes some getting used to all these disks being thin-provisioned on host storage automatically – I prefer PVS vDisks and Write Cache at the moment.

  • Disclaimer as above.

    @Rene: for a pooled catalog, you’ll get a new diff disk every time a VM boots. A background task will remove these disks in time.

    You’re correct that how XenDesktop 5 using Machine Creation Services works is significantly different to how the combination of XenDesktop 4 and PVS works, and imposes different loads on your system. What makes you prefer vDisks and write cache to thin-provisioned diff disks?

  • @Philip; Well, I am new to thin-provisioning (and possible risks of this technique) and “all those autocreated disks” are a bit unnerving to me, whereas fixed vDisks and correctly configured write cache (mostly on persistent disks belonging to the PVS target) will give you maximum control over what happens on which storage repository.
    Having said that – there are consequences for availability as well (PXE-booting is hard to make redundant) which I havn’t completely thought out yet (maybe you can contemplate on that?).

  • @Philip; I just realized that apart from risks as a result from multiple thin-provisioned disks (they could flood your host storage, couldn’t they?) it is also difficult to size; how much storage is needed for – say 30 Windows 7 desktops (pooled/dedidcated) – when they are created by MCS? How do you calculate that?

  • @Rene: sizing your diff disks is something which is very use case dependent. At one extreme, if you’re using pooled desktops and your users are locked down to using a web app which writes only minimal data to the local disk, the amount of space you’ll need per user will be very small.

    On the other hand, if you’re using dedicated desktops and letting developers install whatever apps they like on the VMs, you’ll need a lot more space per user.

    The recommendation here would very much be to run a pilot trial with your users, find out how much space they typically need, and scale up from there.

  • Philip,

    There might be a simple mathematical rule like
    diff disks = yy * xVM
    And I think to establish this rule we need to have more feedback from actual XenDesktop 5 deployment.

  • Yesterday I deployed dedicated desktops with MCS at a customers site, using local storage on XenServer 5.6 FP1. I come up with the following formula for the maximum amount of desktops;

    where available storage=X and master image size=Y

    (X-Y+2*Y)/(Y+16Mb)

    Explanation; You have to divide the available storage (X) minus the master image disk space (Y). MCS creates an additional snapshot plus a base disk so that’s another 2*Y. The remaining space will be filled with diff disk + identity disks.
    I had 271 Gb and I could create 8 desktops (dekstop 9 and 10 failed to be created as I had no free space left). After deleting the original master image I could add a ninth desktop to the catalog with MCS.

    So it would seem that on XenServer it’s not really ‘thin-provisioning’ because the total size of the diff disk is reserved on host storage and not the actual disk space used on the diff disk at the moment of creation.
    With pooled desktops the formula will change however because you’d need an additional diff disk per boot sequence (which would be deleted within 8 hours).

  • Stephane: absolutely.

    Rene: did you select the “Optimize for XenDesktop” option when installing XS5.6 FP1? If so, you should get thin provisioning on local storage.

    You should probably also be aware the XS5.6 FP1 is not supported for use with XenDesktop 5.

  • @Philip; No, we upgraded the XenServer 5.0 host to 5.6 FP1 (as that is the latest version) and missed out on that option. Is it displayed during XenServer installation? Can you configure it after installation?
    Or do you mean the VM optimization feature that we all know (Optimize for XenApp, General Use or manually) – that doesn’t display XenDesktop…..

  • Rene: to get thin provisioning on local storage, you need to change your storage to be ext3 based rather than LVM based. This involves blowing away your storage and starting again, which is why it’s not presented as an option during upgrade.

    If you are prepared to blow away your storage, you can do this from the XenServer command-line and then recreate it as ext3, after which you’ll get thin provisioning.

    And yes, future versions of XenDesktop and XenServer will have better integration here!

  • Hi Stephane,

    Indeed it’s good article, good to read that. Thanks for sharing.

    Regards,
    Shiv