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Raid 5 guestions??
shmokes:
I assume you can use a hotspare with RAID 5 or 6. In any case, whether you're using RAID 5 or 6, you have to replace a drive that goes bad. The hotspare means that you've got a replacement drive ready so when one drive fails, the replacement drive automatically comes online and the array is rebuilt, without any intervention required. That's what I'm guessing from what I've read here, anyway. I don't actually know anything. ;D
patrickl:
--- Quote from: shmokes on February 02, 2008, 12:26:52 pm ---I assume you can use a hotspare with RAID 5 or 6. In any case, whether you're using RAID 5 or 6, you have to replace a drive that goes bad. The hotspare means that you've got a replacement drive ready so when one drive fails, the replacement drive automatically comes online and the array is rebuilt, without any intervention required. That's what I'm guessing from what I've read here, anyway. I don't actually know anything. ;D
--- End quote ---
Indeed, but when you are ready to supply an extra drive in there anyway then RAID 6 would use that extra drive so you have two drives for parity. That means 2 drives can fail and the array is not vulnerable while it's restoring the array from a single drive failure.
Guess it's not that different when the hot spare comes in quick enough and RAID 6 would probably be slower in writing. I'd say RAID 6 is safer though. Even a single extra bad block during or before rebuilding can destroy the entire array with RAID 5.
boykster:
--- Quote from: lcddream on February 02, 2008, 11:36:55 am ---My 3ware 9550sx will email me with any problem that occurs.
--- End quote ---
My 7000 series card do as well.
I'm not all that well versed on the advantage of RAID5 + hotspare vs RAID6; my cards don't support RAID6. I don't even use a hotspare right now, I keep a cold spare ready to swap in.
patrickl:
--- Quote from: boykster on February 02, 2008, 02:04:24 pm ---
--- Quote from: lcddream on February 02, 2008, 11:36:55 am ---My 3ware 9550sx will email me with any problem that occurs.
--- End quote ---
My 7000 series card do as well.
I'm not all that well versed on the advantage of RAID5 + hotspare vs RAID6; my cards don't support RAID6. I don't even use a hotspare right now, I keep a cold spare ready to swap in.
--- End quote ---
I thought that squirrellydw said that his RAID card supported RAID 6.
I have never used RAID 6 either, but with RAID 5 I'm always one step away from a heart attack when the array is rebuilding. If a bad block is found during rebuilding then you potentially could have a double drive failure. RAID 6 shouldn't have a problem with that.
I guess it depends on how quickly it detects a bad block. I always assumed it would only see a block failure when it accessed a specific block. That would mean a bad block could exist on a drive for a long time before it is detected. It might only be while rebuilding the array after a drive failure that it stumbles on a previously undetected bad block on one of the other drives. I suspect that this happened at least once to me. The system reported a single drive failure and when it was rebuilding it suddenly reported a double failure.
I actually mostly use hardware mirroring. I think I have had a dozen or so RAID 5 configurations on our web and file servers over the last 10 years and I got so fed up with all the RAID 5 hassle (backup problems and recovery problems) that I mostly switched to mirroring now.
I have mirroring (double hotswap unit) on my webservers and workstation (on my notebook even) and only use raid 5 on the file server. Mirroring is so much easier to recover and does not depend on any hardware or specific configurations. Besides, I just swap out a disk and I have a backup. I prefer using that in situations where I don' t need a lot of storage.
BTW another issue with backups is protection against deletes and/or accidental changes (ie stupidity or viruses) The ReadyNAS has a nice backup method where it keeps a previous version of all files. On my webservers I use rdiff backup to keep all different versions for over a month or so.
squirrellydw:
Yes, I am planing on raid 6 plus 1 hotspare
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