Can you help me with my software licensing question?
VMware ESX is free for upto 6 cores per CPU only
Vsphere Advanced version is required for 12 CPU cores
does Xenserver 5.5 free support greater than 6 cores per CPU/Socket?
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There isn't a limit on the number of cores per socket, just cores per host.
Just beware that there's a core-per-socket setting in XenServer, only available to paid versions of XenServer. Also, if you're using Windows vms, you've to make sure that there are cpu socket limits on Windows editions.