I recently did a TechTalk discussing XenDesktop Design topics. If you missed it, you can watch the recording. Unfortunately, I didn’t have time to answer the questions during the webinar, but I’ve gone ahead and tried to answer them here. If you have more, please let me know.
Daniel – Lead Architect
Q: Can we cover difference disks at all?
A: Difference disks are simply write cache files that are not deleted upon reboot. Sounds pretty sweet doesn’t it? There are a few concerns with doing this. The difference disk is stored on the Provisioning services server. That means you will put more stress on the PVS network and add additional latency to accessing the write cache as it must cross the network and be managed by the streaming service. Plus, as the difference disk is accessed, this will potentially utilize the Windows server’s system cache, which might un-optimize (is that a word?) the delivery of the vDisk itself (that is if you followed the RAM planning for Provisioning services).
Q: How do I get this ISO file to boot my virtual desktops with provisioning services?
A: You use Provisioning services to create the ISO file via the Boot Device Manager (BDM). You then put that ISO in your CIFS Share for XenServer, which allows your VMs to access the file. Simply select the ISO as part of your DVD Drive configuration and configure the VM’s boot order to boot via the DVD drive first.
Q: While using BDM, how can we use XD Wizard to create multiple STD desktops from a single vdisk.
A: The process is the same, except that you need to make sure your VM template that you use as part of the XD Setup Wizard is configured to boot from the DVD Drive first, and that the DVD drive is configured to use the ISO file. Then all clones will have the same settings.
Q: For mobile, the chart recommends virtual apps. What category would the iPad be classed as? What delivery method is best? I thought that giving the user a full desktop on the iPad would be beneficial.
A: It depends (remember, I’m a consultant J). If your user only needs to get to a single application, why do they need an entire desktop? However, if they need multiple applications, better off giving them the virtual desktop to allow for multi-tasking and the true desktop experience. Honestly, most iPad users will end up with a desktop as they will need more than 1 app.
Q: How can we automate creation of create one-one PVT image desktops , the way we use XD wizard for STD desktop creation
A: You might be able to still use the XD Setup wizard, but it wasn’t meant for this use case (at least in my perspective it wasn’t). In fact, if you are doing private images, you might want to rethink why you need the Provisioning services component? That will just add another layer you won’t need. You would be better off creating a Windows 7 VM. Run SysPrep. Turn it into a template. Then start cloning.
Q: How can I Assign more RAM to DOM0?
A: On XenServer, modify the /boot/extlinux.conf. We typically increase this to 2.94GB. You will see a “label xe” section and within the section is the dom0_mem= parameter. Modify that.
Q: I have a customer with a Xenserver… our application calls IE to run MS Reporting Services and we require a session associated to an IP address. How can i ensure each session has its own IP address?
A: Each virtual desktop must have its own IP address, which should be taken care of by DHCP. Now if you need to have static IP Addresses for your VMs, then you still can use DHCP, just setup static leases.
Q: Is it better to cache on the virtual desktop on a second disk like 5 gig of disk instead of on PVS ?
A: Yes, because going back to PVS adds network traffic to the PVS server (which it already has a lot of), plus the traffic goes through the PVS streaming service, which might impose latency on streams going out. Also, if the write cache is on the PVS server local disk, you won’t be able to have HA from a PVS perspective as other PVS servers don’t have access to the write cache. Finally, as PVS will have to read sections of the write cache, this will make the entire RAM planning aspect for the PVS design much more difficult as the number of write caches is an unknown. But with vDisk images, we know you need X amount of RAM per vDisk to optimize the Windows Server 2008 system cache process.