This operation can not be performed because the specified virtual disk could not be found [XenServer error]

Working on a long term project I encountered the above error. Research online stated that all you needed to do was empty the "DVD" drive and the error would go away. All well and good ... unless it's happening when you are trying to install a VM, then not so good.

The funny thing is that I didn't see anyone posting the real solution to this so ...

In the case of most of us we mount all kinds of things as SRs including a few CIFS stores since the ISOs that we need are out on Windows shares. Ah but what credentials did you use to connect? Like me you probably used your "admin" account and that's fine but in many cases (especially in enterprise environments) we have to rotate passwords every so often (YMMV). XenServer of course doesn't know this and blindly uses the old password. Guess what, there is no way to change the username/password information used for the CIFS library easily.

To fix the actual issue do the following:

1. Open/Start XenCenter.
2. Highlight the host that is reporting the issue.
3. Go to the Storage tab.
4. Get the properties of the ISO library that is causing the issue.
5. Detach the ISO library.
6. Go to the left window where the old SR is still listed, right click and select "Forget."
7. Back under the Storage tab, click on "New SR" button and create a new SR like the previous one.
8. Verify that the error no longer appears when trying to mount the ISO.

There you go, good for the next 90 days (or so). :D

One last tip: to prevent this a dedicated service account is recommended. One that (as allowed) is not required to have it's password changed regularly. Depending on security policies where you are this might be a simple thing to get or more complicated. Good luck.

Building XenApp Servers in 30min

So you're tasked with setting up multiple servers and don't want to be there till the wee morning hours. Significant others can be such a pain! :D

Some will say that making a "gold image" of a XenApp server is the best way to do this but I find there are issues with the xenappprep/sysprep method. One of them is that with that method there is a lot of post reset "cleaning" that needs to be done. With that it can make the whole process longer than you might feel it should have taken.

In the method I'll outline shortly we will still be using a template with an OS pre-installed but from there we will be doing things a bit different. One thing that is assumed is that we will be joining the server(s) in question to an existing farm. If you are setting up a new farm then this all should be after the initial server is setup and your farm is communicating properly. DO NOT try and use this process for setting up a first server and farm.

Prep Work

Okay first you have your farm running (first DC is up and you have access).
Next you have a template for a bare bones Win 2008 R2 Server that is OOBE set.
Finally you have copied the MF20.dsn from the first server to the location that the install media is.

Let's Get Going

Create a VM from template and configure what's needed (vCPU, Mem, Storage, IP, Name, Activate!!!!) and make sure it connects to domain and is accessable (basic stuff I know but always good to remind yourself).

Once the server is up and running, oh and you can do several of these pretty easily at the same time, time to put in roles. The key to doing this fast is scripting and knowing what needs to be added. Here are the basic roles that need to be added:

Add-WindowsFeature XPS-Viewer -restart -logPath C:\role_install.log
Add-WindowsFeature SNMP-Services -restart -logPath C:\role_install.log
Add-WindowsFeature AS-Net-FRAMEWORK -restart -logPath C:\role_install.log
Add-WindowsFeature GPMC -restart -logPath C:\role_install.log
Add-WindowsFeature RSAT-ADDS-Tools -restart -logPath C:\role_install.log
Add-WindowsFeature Desktop-Experience -restart -logPath C:\role_install.log
Add-WindowsFeature RDS-RD-SERVER -restart -logPath C:\role_install.log

The server will need to reboot about two times since Desktop Exp and RDS both need reboots to complete. this should happen even if the -reboot switch would normally suppress it so don't be alarmed.

Once the roles are in place we install XenApp. In this I usually install session-host servers and not full. They use a bit less memory and are a bit more "hardened" as the tools that are normally there are not. No console or policy tools so if something "bad" should happen, the server can't be used to exploit further into the farm.

So with that in mind, this is what I use to install:

Start-Process "\\<server>\<volume>\<source dir>\XenApp Server Setup\bin\XenAppSetupConsole.exe" -ArgumentList /install:XenApp /exclude:XA_Console /Advanced /logfile:C:\xa_install.log -NoNewWindow -Wait

For those that want full server capability, remove the  /exclude:XA_Console part from the command line. 

Then to configure:

Start-Process "C:\Program Files (x86)\Citrix\XenApp\ServerConfig\XenAppConfigConsole.exe" -ArgumentList /ExecutionMode:Join /ImaWorkerMode:True /ZoneName:<zone> /DsnFile:[drive]:\MF20.dsn /OdbcUsername:[dsadminuser] /odbcPassword:[password] /AddAnonymousUsersToRemoteDesktopUserGroup:False /AddUsersGroupToRemoteDesktopUserGroup:False /ProhibitShadowing:False /ProhibitRemoteControl:False /ForceShadowPopup:False /ForceShadowLogging:True /CustomXMLServicePort:8080 /CreateAnonymousUserAccounts=False /RemoveAnonymousCitrixAccounts:True /LogFilename:C:\xa_config.log -NoNewWindow -Wait

Again if you want a full XA server with all the tools and capable of being a DC, remove /ImaWorkerMode:True  from the command line.

A couple of things about the configure part. The DSN file should be located on a mapped drive, UNC paths don't seem to work well for that setting. Coulld be just bad luck on my part but then again ...? The script also does something that I found hugely useful, it eliminates all Anon accounts that seem to always be added no matter what you say during a GUI install. Finally being able to preset the XML port prevents a common mistake of setting the wrong port during a typical setup.

After that you should have a "clean" and brand new XA server ready for work!

Additionally you will want to run HRP03 with something like:

Start-Process "msiexec" -ArgumentList "/p [drive]:\<source>\XA650W2K8R2X64R01.msp /qn /passive /norestart /Liewa C:\hrp_install.log" -NoNewWindow -Wait

You will note that though I said this all is scripted, I didn't provide the script ... well I'll leave that to the class to figure out. :D

Peace.