We will be setting up a system as the following (on a Dell PE R510 with a PERC H700 (LSI2108) 512MB-BBU SAS HBA):

Disk Bay 1
2xHDD RAID 1 Virtual disk A

Disk Bay 2
8xHDD RAID 10 Virtual disk B
4xHDD RAID 10 Virtual disk C

Now with the PERC controller, you can create "disk groups", then virtual disks within those groups. The only requirement with disk groups is that all virtual disks within that group are of the same RAID level. So, with respect to the two virtual disks in bay#2, is there a benefit in creating one group to house both virtual disks or should we create two separate groups, one for each RAID 10 VD? Anyway, which is better, or does it even matter?

  • The RAID arrays suggest those are 15K RPM HDDs. I would suggest you use SandForce-based SSD in RAID1 instead, they are much more suited for DB work. – Mircea Chirea Oct 6 '10 at 2:56

Which is better and whether it matters depends on what you want to do with the disk capacity.

If you need to totally isolate the IO between the three virtual disks then having three RAID groups makes sense. If you have IO requirements for individual volumes that will benefit from being able to make use of more peak IO\Bandwidth than can be delivered by 8 disks then you may be better off making one larger RAID group (to get all the spindles into one pack) and splitting that up into the multiple virtual disks.

  • Thanks for the reply! This will be a small database server (MSSQL2008). The virtual disks would be used as follows: A: OS (WS2008R2), B: DB-Data, C: DB-Logs. What would be recommended as the better approach given this purpose? BTW, I've seen tons and tons (and tons :) of discussions about many RAID setup aspects but few that deal with disk "groups". – Aaron Jun 19 '10 at 20:46

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