smithdoerr said:
So I'm in the market for a new motherboard since the old one
seems to be dead. My question is, will the new motherboard be
able to access the old raid 0 array? Would the new motherboard
need to have the same raid controller as the old to do this?
I run weekly backups onto nas so all my important files are safe
in case I have to reformat my drives but there are a few odds and
ends as well as a few files that were created since the last
backup that would be nice to recover if possible. If not, no big
deal but I'd like to if possible.
RAID migration works best, if the chip used on both motherboards,
is made by the same manufacturer. And preferably, not too many years
apart. Perhaps drives connected to Intel ICH7R, ICH8R, ICH9R, ICH10R
would be interchangeable. Or moving the drive from an old Nvidia
Mediashield motherboard, to a new Nvidia one (Mediashield is Nvidia RAID).
But moving a Mediashield RAID0 over to Intel, probably won't work.
As far as I know, there are no standards for RAID metadata. Each
company defines their own internal standard. There have been
a couple cases, of chipsets where a deal was made with Promise,
for a FastTrak BIOS module, and then the metadata type would
be Promise.
Tomshardware did a test years ago, and tried to move a RAID
array between companies, and got the results as described.
Basically, only RAID arrays moved between "same company"
chipsets, would work.
With some effort (for technical points), RAID 0 would be
the easiest format to fudge. The metadata sectors are likely
up near the end of the disk (I've tested that here). You could
prep a pair of disks on the new motherboard, then use a
Linux LiveCD and the "dd" program, to copy the user data
from each old drive, to the equivalent new drive. There
are two details to get right - the declared "stripe size"
on the new RAID metadata, has to match. And you have to
successfully copy old_disk_0 to new_disk_0, old_disk_1 to
new_disk_1, and then it should work. (Being careful to not
overwrite the metadata up near the end of the disk.) So
with a new pair of disks, you could (safely) attempt to
hack this, but in the time it takes to do it, you could
have completed a re-install.
http://upload.wikimedia.org/wikipedia/commons/thumb/9/9b/RAID_0.svg/150px-RAID_0.svg.png
The metadata should be defensively designed. When the metadata
is written, the "declared" capacity of the array, is smaller,
by the number of megabytes of "slack space" provided, so the
metadata won't get overwritten. So the metadata protects itself,
by telling the OS the array is slightly smaller than it really
is, and that is how the metadata avoids getting overwritten.
Normally, disks aren't used, right up to the end, due to a
few usages defined for the end of the disk (I think Dynamic
disks keep about 1MB of data up near the end as well, to give
another example).
And this is yet another reason, for doing frequent backups on
RAIDs. The migration problem...
Another possibility, is any data recovery software that is
known to handle RAID arrays. You could probably take the
pair of disks, to a working computer, and have the data
"de-striped" and put onto a single drive.
If you're clever, you can even do that yourself
It's a
relatively simple pattern and all the copying could be done
with "dd" and the "seek" and "skip" options. The MBR will
still be OK, as it will be declaring the correct
partition size and file system type. The MBR is sector zero,
and will be in the first stripe of disk 0, and when copied,
will be in exactly the right place. To move a RAID
array to a twice-as-big single drive, is a purely
mechanical sector transfer pattern. Not many stripe
sizes are used (perhaps 64K or 128K). And you can tell
which disk is disk_0 in a RAID0 pair, as the MBR sector
has AA55 as the last two bytes of sector 0. A copy of the
first sector, followed by examination with a hex editor,
will tell you whether you're looking at disk_0 or not.
Loads of fun
For an OS, to do that, you can use a Linux LiveCD, like
Knoppix or Ubuntu. They'll both have copies of "dd".
There is a Windows port of "dd" available as well.
"Seek" and "Skip" are documented here. You can move
any arbitrary blocks from one disk, to an arbitrary
start address on another disk. Great for surgery.
The only deal with the Windows version, is if the
OS prevents you from accessing something (i.e. preventing
you from erasing C: by accident). Doing it from Linux,
is less of a problem.
http://www.chrysocome.net/dd
Paul
