What happens with a Raid 5 when the controller fails?
in [Storage]
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From: mscotgrove on 21 Jan 2008 11:44 On Jan 21, 2:43 pm, Arno Wagner <m...(a)privacy.net> wrote: > Previously Robert Wegner <rob...(a)gmx.net> wrote: > > > Hi there, > > i've got an old storage server here, running W2k, with a promise > > pci-card raid controller. The controller hosts a raid 5 array and it > > is 4 or 5 years old, so i guess it isnt built any more. So, i > > wonder, what if the controller fails and i can't buy exactly the > > same one? Can i simply build in any new raid5-capable > > controller-card? Or does the controller has to be compatible in some > > way (to the old card)? > > The problem is that the RAID superblock is not standardized and hence > it it unlikely to work with a different controller, unless the > manufacturer specifically claims compatibility with your present > controller. In fact not even the place the RAID superblock is found > in, is standardized. That is also the reason why, when using hardware > RAID, you should have a spare controller of the same model. > > > Or is the data lost? > > RAID5 is easy to recover for professionals. There is also an other > option: dmraid (part of Linux software RAID) can assemble and use > arrays from several different fake-RAID (software-RAID on a card, > which is likely what you have) controllers. This may allow imaging the > RAID under Linux, regardless of filesystem on it. > > My advice is to replace the controller after a full backup and > to recreate with a new controller, of which you get two in > order to have redundancy. Or to move to software-RAID, which does > not have this limitation. > > Arno Have I got the wrong end of the stick, but Superblock is a Unix term, and not Windows? I have 'struggled in the past with Unix disks as they all seem different relating to superblocks etc. The question though relates to W2K server - is Superblock relevant here? Again, please tell me if I am wrong, but I always thought a RAID disk logically looked like normal big disk that just happens to be fault tolerant. Michael
From: Folkert Rienstra on 21 Jan 2008 16:04 Odie Ferrous wrote in news:47942D3F.8FEDF010(a)hotmail.com > Folkert Rienstra wrote: > > > > Robert Wegner wrote in news:YtSdnTQnaZtoQA7anZ2dnUVZ8s6inZ2d(a)giganews.com > > > Hi there, > > > > > > i've got an old storage server here, running W2k, with a promise pci-card > > > raid controller. The controller hosts a raid 5 array and it is 4 or 5 > > > years old, > > > > > so i guess it isnt built any more. > > > > Right, why check if you can guess, right? > > > > > So, i wonder, what if the controller fails and i can't buy exactly the > > > same one? Can i simply build in any new raid5-capable controller-card? > > > > Sure, why not? > > > > > Or does the controller has to be compatible in some way (to the old > > > card)? > > > > Nope. > > > > > Or is the data lost? > > > > Very likely. > Not at all likely, actually. Gee, not at all, Odiferous? > But your answers are always designed to be > helpful and sympathetic, aren't they, Folkert? Like yours are, Odiferous. > Rob - any reputable data recovery company Now what does that say about you, Odiferous? > should be able to recover your array without any problems. Which Odiferous just offered to do for free, right, Odiferous? > > > Which is why you have backups that you can roll back. > > > > > > > > Thanks and best regards, rob > > > Duncan
From: Folkert Rienstra on 21 Jan 2008 16:04 Arno Wagner wrote in news:5vjpclF1mv66iU1(a)mid.individual.net > Previously Robert Wegner <robweg(a)gmx.net> wrote: > > Hi there, > > > i've got an old storage server here, running W2k, with a promise > > pci-card raid controller. The controller hosts a raid 5 array and it > > is 4 or 5 years old, so i guess it isnt built any more. So, i > > wonder, what if the controller fails and i can't buy exactly the > > same one? Can i simply build in any new raid5-capable > > controller-card? Or does the controller has to be compatible in some > > way (to the old card)? > > The problem is that the RAID superblock is not standardized and hence > it it unlikely to work with a different controller, unless the > manufacturer specifically claims compatibility with your present > controller. In fact not even the place the RAID superblock is found > in, is standardized. That is also the reason why, when using hardware > RAID, you should have a spare controller of the same model. > > > Or is the data lost? > > RAID5 is easy to recover for professionals. There is also an other > option: dmraid (part of Linux software RAID) can assemble and use > arrays from several different fake-RAID (software-RAID on a card, > which is likely what you have) controllers. This may allow imaging the > RAID under Linux, regardless of filesystem on it. > > My advice is to replace the controller after a full backup and > to recreate with a new controller, of which you get two in > order to have redundancy. Or to move to software-RAID, which does > not have this limitation. Or you could just make backups, eh, babblebot? > > Arno
From: Arno Wagner on 21 Jan 2008 19:28 Previously mscotgrove(a)aol.com <mscotgrove(a)aol.com> wrote: > On Jan 21, 2:43�pm, Arno Wagner <m...(a)privacy.net> wrote: >> Previously Robert Wegner <rob...(a)gmx.net> wrote: >> >> > Hi there, >> > i've got an old storage server here, running W2k, with a promise >> > pci-card raid controller. The controller hosts a raid 5 array and it >> > is 4 or 5 years old, so i guess it isnt built any more. �So, i >> > wonder, what if the controller fails and i can't buy exactly the >> > same one? �Can i simply build in any new raid5-capable >> > controller-card? Or does the controller has to be compatible in some >> > way (to the old card)? >> >> The problem is that the RAID superblock is not standardized and hence >> it it unlikely to work with a different controller, unless the >> manufacturer specifically claims compatibility with your present >> controller. In fact not even the place the RAID superblock is found >> in, is standardized. That is also the reason why, when using hardware >> RAID, you should have a spare controller of the same model. >> >> > Or is the data lost? >> >> RAID5 is easy to recover for professionals. There is also an other >> option: dmraid (part of Linux software RAID) can assemble and use >> arrays from several different fake-RAID (software-RAID on a card, >> which is likely what you have) controllers. This may allow imaging the >> RAID under Linux, regardless of filesystem on it. >> >> My advice is to replace the controller after a full backup and >> to recreate with a new controller, of which you get two in >> order to have redundancy. Or to move to software-RAID, which does >> not have this limitation. >> >> Arno > Have I got the wrong end of the stick, but Superblock is a Unix term, > and not Windows? Yes. As Unix did RAID long before Windows existed, it is called a "superblock". But it is not Unix specific, it just means "the block where geometry information and such is stored". > I have 'struggled in the past with Unix disks as they all seem > different relating to superblocks etc. That would be the filesystem superblock. Similar task, but no connection to RAID. > The question though relates to W2K server - is Superblock relevant > here? Yes. > Again, please tell me if I am wrong, but I always thought a RAID disk > logically looked like normal big disk that just happens to be fault > tolerant. On the computer side, yes. But on the disk side, meta-information needs to be stored somewere. This is done in the RAID superblock and it will be hidden from the computer by the RAID layer. Arno
From: David Lesher on 23 Jan 2008 12:52 One option would be to buy a spare Promise card now, before you need it.... That said... you still need backups... -- A host is a host from coast to coast.................wb8foz(a)nrk.com & no one will talk to a host that's close........[v].(301) 56-LINUX Unless the host (that isn't close).........................pob 1433 is busy, hung or dead....................................20915-1433
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