RE: SQL Server, SANs and Virtualisation

One Orange Chip

Points: 26778

January 11, 2009 at 5:24 pm

Perry Whittle (1/11/2009)
homebrew01 (1/10/2009)
Perry Whittle (1/10/2009)
homebrew01 (1/10/2009)
Our plan is to take our 2 heaviest hit SQL servers and put them onto their own physical machines running VM. They will have the VM overhead, but not sharing with any other servers. We like the VMotion DR type aspects.
if you're putting each VM onto a dedicated box of their own its pointless spending the $$$$$$$ on the vmware licences, they may just as well be physical sql servers straight off. No problem with storing a 1TB db on the SAN at all, better in fact i would think.
No DR or other advantages with using VM in this case ?
possibly but for the cost of the licences you could possibly find other ways. The general rule of thumb is if you get to the point where you dedicate a whole host to a VM it may as well be a physical machine

One other thing to test for your larger database is the effect of parallelism waits CXPACKET on performance. My experience with VM's is that parallel processing is a performance killer rather than a performance enhancer. The reason for this is that the VM host software is configured to manage context switching and the multiple threads are no longer going against multiple processors necessarily. Generally speaking, I see much better performance from my VM's be setting the Max Degree of Parallelism to 1. If your 1TB+ database currently benefits from parallel processing, you definately want to test what the performance will be like under a VM.