Dell Perc 6 RAID options (Vmware)

[Django x2]

Hi all,

Just accquired a Dell CS PowerEdge that has 12TBs in it.

I didn't realise at the time, but these are span across two Dell PERC 6Ir controllers.

I seem to be able to create a VD in one of the controllers for 8 of the drivers, and another VD in the other controller for 4 drives

RAID 10 is what I've gone for, but not sure if this is the best config for VMware.

I wondered if there was a way to merge the two controllers together so you could see all 12 physical disks in the one screen and configure the RAID through there.

Also, any preferred settings re block size, write-back / through, etc, would be great. Thanks

 

[Knubje]

Hi,

I think that particular Dell PERC controller is limited to 8 physical disks. I don't know any way of merging them, it's a fairly basic controller.

As you are using VMware I assume you will be formatting the LUN with VMFS volumes from those disks. The block size on VMFS-5 is 1Mb. The stripe size of the disk isn't probably going to make much difference unless you need the most critical edge and requirement for performance gain. I'd stick with 64k or 128k.

Write back will slightly increase performance but has the risk of data loss if the host loses power and the controller battery is knackered. Write-through will be the default and is safer. Depends on the cache of the controller which I'm really not sure without looking all the specs up.

If it were me I'd keep the 8 disks and go for RAID10 giving you 3,579 GB and ~770 iops for performance. For the 4 disks I'd go for RAID5 (~2.7GB) and have it as slow capacity disk giving you ~260 iops. Making assumptions that they are 10k SAS disks.

Is this for a production environment or dev/test lab? If it's the latter then you could play around with IO Meter and the stripe size of the VD but I think the gains would be minimal given the controller.

Hope this helps? Happy to help if not!

 

[Caged]

Nobody can really help you until you say what workloads you are going to be running.