We have implemented 16 presentation 4 servers on ESX3.0.1
First impressions were pretty average with a lot of user compaint in regard to performance. We do however have many users that open 5 or 6 Excel spreadsheets that are more than 20 MB in size. We also had Citrix virtual servers on the same physical box as other production virtual servers
All Citrix servers run the basic app package (office, adobe etc) + around 12 custom busniness applications such as finance apps, document storage, and bespoke apps.
An article has just been released by VMware that proposes excellent Citrix performance on ESX3 on HPDL585 hardware which we are using. The test involved having only 8 virtual machines on each physical box and physically assigning one CPU core per VM.
We have since spread all 16 presentation servers amongst two dedicated physical boxes and performance has increased significantly.
We are now trialing asigning a physical CPU core per VM on one physical box to see how this goes, will let you know.
We have thrown out the idea that you can put 10 - 20 virtual Citrix servers per physical box.
We have also found that the user cut off limit for each presentation server is about 16-18 users.
Any user who was used to working on apps at remote site love Citrix on ESX, even with our average performance originally.
Any Head Office user who is used to working on fat applications tend to notice the performance reduction more.