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From: Folkert Rienstra on 22 Jan 2008 13:19
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.

Any RAID is, if you know how to interprete the Raid Controller metadata.

> 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.

Like there is a huge difference on the disk side between hardware and
firmware assisted RAID but not between the firmware assisted RAIDs.

> 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 recre-
> ate with a new controller, of which you get two in order to have redund-
> ancy. Or to move to software-RAID, which does not have this limitation.
>
> Arno
From: Arno Wagner on 29 Jan 2008 07:14
Previously DonLogan <navajo(a)neonfeather.com> wrote:
> Arno Wagner <me(a)privacy.net> wrote:

>>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.

> Yes he has a working Raid & wants to migrate before failure. And he's
> waited too long.
> So how does he do this backup / replace controller / use two?
> "recreate"? Not easy. Or do Promise offer an data upgrade or
> compatibility option?

Very simple: For Backup he uses his standard backup method. If
he does not have one, the data is obvisouly worthless, and he
can just erase it. (Well, or right now establish a backup
nethod....)


>> Or to move to software-RAID, which does
>>not have this limitation.

> again - migration path?

See above.

Remember, RAID is abaout availability. It is not substitute
for backup.

Arno

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