We've just purchased an MSA 2312 fc with 4 enclosures one enclosure filled with 1TB SATA the 3 filled with 450GB SAS
I was wondering about the best way to carve up the SAS drives. The storage is going to be used completely for a test environment connected to 2 stand alone ESX servers.
So far we've decided to divide the 36 SAS drives into 2 large vDisks of raid 50 with 2 sub disk groups in each, each containg 2 lots of 9 disks for the raid 5. I think this will give us decent mix of performance and protection - only downside I can see are rebuild times. Would we be better to create smaller vDisks with smaller disk subsets? As I said as this is just for test environment we don't need to go over the top on performance or protection just need to find a happy medium.
If you have the time run some i/o tests with the setup you propose and using fewer disks in your vdisks. This array/disk model is rather new and there might not be enough feedback. Every array has its own capability regarding the number of disks in a RAID group that will perform best. The sales people probably told you that the more disks you put in the raid group the merrier. I have found out that this is nothing more than bad sales pitch. As you test out the raid groups, when adding more physical disks in a group you will notice a performance increase when you start with a few disks and then you gradually add more disks. But after a certain number of disks you will see the perfromance leveling off and then as you add more disks, the performance decreases. The optimal number of disk in a raid group varies with each array make/model/disktype and it depends on the number of back-end i/o buses, the array processor power, cache memory, raid type etc.
