Ken Schneider wrote:
On Fri, 2006-03-24 at 15:17 +0100, Per Jessen wrote:
All,
probably a little OT here, but I _am_ using SUSE Linux :-)
I'm trying to work out the optimal (or near-optimal at least) RAID configuration of a 24-disk array. The array comes with two redundant RAID controllers each with six SCSI channels. These controllers allow all kinds of RAID0/1/5 configurations, but no RAID6.
I want the array to be able to survive a two disk failure, so RAID6 would be the obvious choice, but ...
So I'm sort of looking at choosing between -
- using plain software RAID6 and ignoring the hardware RAID facilities of the array. - using the hardware controllers to build a combination of RAID0/1/5 that'll give me the two drive failure survivability.
I've had a look around the web, but googling for "two drive failure RAID" almost always leads to someone talking about RAID6 ...
So, opinions/suggestions?
Search around some more for an array controller that provides raid 6, it is the only way you will get "two drive failure" and make sure -all- of the drives are hot swappable. Employ alert notification using SNMP for when a drive fails and have spares on hand at all times. Also look at: http://www.acnc.com/04_01_06.html for more info.
Actually, if you setup RAID 10 correctly (striped mirror sets) then you can have half of your drives fail, so long as you don't have two in the same mirror set go at once. Going with RAID 5 or 6 incurrs a write perofrmance penalty which may or may not be tolerated by the app. This can be overcome by a good amount of battery backed cache on the front end though. Essentially, you have performance, reliability, cost as concerns: pick any two and those will drive your decisions. - Herman