RAID and IOPS and VDI

On 8 January 2013 by Pete Petersen
RAID 10

Image source: http://www.thedatarescuecenter.com

 

RAID 5

Image source: http://www.thedatarescuecenter.com

There is some controversy about the right RAID in your storage. And the controversy is warranted because it depends. It depends on your application, your drive configuration, your hardware (including the controllers), and whether you’re running local (direct-attached storage, or DAS), or are on shared storage (storage-area network, or SAN).

Let’s say, for instance, that you have a 3.6TB requirement for your VDI implementation. As we know, the better the storage performance, the better the VM/VDI performance. If we use 26 300GB 15K SAS drives in a RAID 10, we should get somewhere in the neighborhood (with ideal hardware, controller, network, etc.) of 3020 IOPS. Whereas if we went with RAID 5, we could use 14 300GB 15K SAS drives, which gives us 975 IOPS. Compare these two figures:

RAID 10 IOPS

 

RAID 5 IOPS

 

So let’s take that one step further and go down, as stated in a couple of articles (see end of this post for references), go down to a 4-drive RAID 10 array and a 4-drive RAID 5 array, and compare those. As stated in George Ou’s article, running with a 4-drive RAID array gives very different results than otherwise may be expected.

Bottom line: Do some homework. There isn’t a single solution that works in all scenarios–even for VDI. Since VDI generally has higher storage capacity requirements, in a SAN scenario, and often utilizing DAS, RAID 10 will server you better.

External References

How to get the most out of VDI IOPS

 

RAID 1+0 is the Cadillac of RAID

Comprehensive RAID performance report

iops calculator

RAID

IOPS

Internal References

Flash-based Storage Changes the VDI Story

Big Storage Decisions Coming for Organizations Moving to VDI

The Case for Local Server Storage

VDI Storage . The Secret Critical Component