What happens with a Raid 5 when the controller fails?


R

Robert Wegner

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)?
Or is the data lost?

Thanks and best regards, rob
 
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F

Folkert Rienstra

Robert Wegner wrote in news:[email protected]
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.
Which is why you have backups that you can roll back.
 
O

Odie Ferrous

Folkert said:
Robert Wegner wrote in news:[email protected]


Right, why check if you can guess, right?


Sure, why not?


Very likely.

Not at all likely, actually. But your answers are always designed to be
helpful and sympathetic, aren't they, Folkert?

Rob - any reputable data recovery company should be able to recover your
array without any problems.

Which is why you have backups that you can roll back.


Duncan
 
M

mscotgrove

Not at all likely, actually.  But your answers are always designed to be
helpful and sympathetic, aren't they, Folkert?

Rob - any reputable data recovery company should be able to recover your
array without any problems.


Duncan
--
Retrodatawww.retrodata.co.uk
Globally Local Data Recovery Experts- Hide quoted text -

- Show quoted text -

RAID 5 is a standard http://en.wikipedia.org/wiki/RAID Therefore it
will not be hardware dependant and so someone will always beable to
recover the data

Michael
 
A

Arno Wagner

Previously Robert Wegner said:
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
 
M

mscotgrove

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.


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
 
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F

Folkert Rienstra

Odie Ferrous wrote in
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?
 
F

Folkert Rienstra

Arno Wagner wrote in news:[email protected]
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.


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?
 
A

Arno Wagner

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
 
E

Eric Gisin

Yes, but it refers to the second block (after boot) of a partition. [wikipedia]
I have never heard superblock and RAID used together.
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".
****ing revisionist. RAID was coined in 1988 at Bezerkly.
That would be the filesystem superblock. Similar task, but no
connection to RAID.
There has never been a disk superblock in UNIX, moron.
 
F

Folkert Rienstra

Arno Wagner wrote in news:[email protected]
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.
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.
 
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D

David Lesher

One option would be to buy a spare Promise card now, before you need it....

That said... you still need backups...
 
D

DonLogan

Arno Wagner said:
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.


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

again - migration path?
 
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A

Arno Wagner

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....)

again - migration path?

See above.

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

Arno
 

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