Rolling out updated Citrix VM Template

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I have updated our Citrix VM Template:

• Added CD, left disconnected
• Updated Tools, included Memory Manager (aka Balloon Driver) -- after reviewing this time and again with various engineers, I have come to several conclusions:
• a lot of the info out there is still based on ESX 2.x
• The Balloon Driver is a safety net, which should not be normally called
  on when designed properly
• when in doubt, and until proven otherwise, go with the standard package
• Tweaked the service controls
• Added PowerShell 1.0 (I'm becoming a big fan of PS scripting)

An Interesting Day with Citrix Load Evaluators

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Ever have one of those days? Well today was it for me! We run XenApp 4.5 in 2 geographic production Zones. I get an urgent page from support that EVERYONE hitting one of our Zones was getting "... servers are reporting full load and cannot accept your connection ..." EEK!

More on Citrix Load Evaluators

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Well, most of feed back I received from other industry players confirmed my initial suspicions... counters based on Windows Perf Counters where Windows is a VM are not reliable. A local area architect, who is not married to any one technology, summed it up nicely:

"You have touched on something that is inherent to the virtual world: the performance counters are always wrong. Exactly how wrong, that is debatable. In the past, I have used empirical numbers to control load. That means keying off of something like user count, memory utilization, or page swaps. It isn't an exact science, but some testing should give you the right mix."

Citrix Load Evaluator Rules in a VM

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I mentioned in my previous post that one of my VMs was pegging at 100% of the vCPU, but the Windows Task Manager was showing only spikes (although a lot of them), and my Citrix load value for that server was in the 7200 range. Of course, the system was crawling and unusable for customers.

Update on My Citrix VMWare Machines

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Ok, if you have been following my blog, you know I have been researching and building the best possible Citrix VMs to run on my ESX Hosts. Granted, XenServer might be better for XenApp, but we work with what we have, and I have ESX 3.5.

I currently have 4 production VMs running, 2 in each production Zone. The first two in DataCenter1 went live about a month ago... and churn nicely. They will routinely show a load evaluation of 10000 (Full Load), and the 1 vCPU Utilization is fairly high (based on vCenter stats), but no complaints from users. Initial test = PASS.