sizing a SAN

[aleceiffel]

I currently have roughly 20 servers running various apps like exchange, SQL servers, file servers etc.. all using DAS for storage. I am looking to virtualize a large portion of these using VMware ESX and put all the machines on shared storage (looking at SAN/iQ from lefthand networks). Does anyone have any recomendations on how to size a SAN for performance? I am concerned about attaching all these machines to one storage device and having the performance on all of them suffer. Currently, I'm considering using performance monitoring in Windows to get the peak values for the physical disk\disk transfers/sec counters on all the systems durring a work day, adding all of them together and getting a SAN device that handles that many IOPS but that may be overkill or not enough.

Does anybody have any suggestions or articles that I should check out?

Thanks

 

[RMGBELGIUM]

as you already described, that is the way sizing is done
knowing how many IOPS your environment is doing is one thing,a second thing is response time or throughput.This will also have impact on the protocol you will be using ( iscsi or fcp ).Performance is mostly based upon your number of spindles.Better to have 20 disks of 72 Gb then 10 of 144 Gb. I think it would be a good idea to collect counters,look at the statistics of your databases and have some storage vendors propose a solution based upon your collected counters.

rgds,

R.

 

[NickFerrar]

20 servers consolidated into say 3 VMWare boxes isn't going to stress a SAN. Assuming you're fibre attaching them then you don't really need to worry about them affecting each other (it's highly unlikely you'll saturate the SAN bus).

The contention worry would come in if you have different VMWare ESX servers sharing the same storage group (which I'd avoid), if you have a dedicated storage group on the SAN per VMWare ESX server then you really just need to make sure each storage group gives you the IOPS required for the VMWare server using it.

Not sure how you configure your DAS but if you're sharing OS and application volumes onto the same RAID set it would likely be overkill to just add up all your current DAS IOPS peaks and spec a SAN storage group to cover that.