Why do two VMs with the same build as six others run slower and freeze up???

[Ubuntu111]

I manage a farm of eight XenApp 5.0 Citrix servers. These servers are all VMs that reside on the same ESXi 5 hosts. All are on Windows Server 2008 SP 2. All have the same amount of CPU and RAM resources. All have the same apps with the same versions installed. All were built using the same provisioning process.

For some reason the two newest ones that were provisioned freeze up and have latency issues.

What are some things I should look at? I didn't see much in the event logs and the TS settings are the same on all servers.

Thanks!

[marcelo_soares]

Check for disk latency on the disk controller (are all VMs residing on local disk?). If local: http://kb.vmware.com/kb/1007688

But this KB is more detailed: http://kb.vmware.com/kb/1008205

20ms for sustained amount of time is already too much.