On Friday 24 March 2006 9:52 am, Per Jessen wrote:
Jon Nelson wrote:
http://en.wikipedia.org/wiki/RAID5 It's really very good.
Hehe, I know - been there already. It was very informative, but I didn't see much on the two drive failure situation.
I prefer Linux's software raid to most hardware raid - I've experienced several problems with hardware raid but not with software raid, and the talk about hardware raid being faster isn't backed up with statistics or facts.
I like Linux' software RAID too - I use RAID1 all over the place. The one thing hardware RAID (with battery backed cache) does is plug that one little hole that software RAID cannot. I can't quite remember what it is, but AFAIR, in case of a power loss, there is a small risk of screwing up a software RAID5 array.
The reason I'm looking at the hardware RAID using this array is simply cost and ease-of-use - these 2nd hand Compaq Storageworks arrays are almost being given away and they're hot-plug everything. Get one of these, and perhaps a 2nd one for spareparts and you're set storagewise for quite some time.
With 24 disks you could go with a fairly complicated but almost unbelievably robust setup, and in fact with 24 disks if you can afford the space you can mix some mirroring up in there.
I feel fairly certain mirroring will be part of it, yes. Space isn't too important - if I can make 1Tb out of it and still be able to survive a two-drive failure, I'll be quite happy.
/Per Jessen, Zürich
Go with Jon's suggestions. The only data loss you'll suffer with software RAID is if all power is lost at once and the data that is "in flight" to the drive disappears. The hardware way with battery backup on controllers will eliminate that risk. Best of both worlds is designing a hardware RAID setup that you can layer a software RAID on top of that minimizes all those risks! Stan