Moving RAID set - Help please

Desmo · 10-01-2008, 12:38

Seeing as I'm having problems with one of the Macs here (which happens to be the main file server for jobs) I'm looking at moving the jobs discs to another machine. I'm also thinking of possibly putting them onto a spare PC I have.

Now, in the Mac I currently have two drives that are RAID mirrored. If I move them to the PC, will they just work? Even if I just use one drive to start with, does that have all the info? Or is it because they're mirrored, they still need to be in a pair? Although that sounds daft as their wouldn't be any point in mirroring if you couldn't recover from one working drive.

Also, can you tell that I don't really know what I'm talking about when it comes to RAID stuff?

Daz · 10-01-2008, 12:46

RAID only protects you from disk failure (ie, availability), certainly with a the more complicated RAID types it doesn't save your data from server failure, or at least, it's not guaranteed to.

Short answer is it depends on the RAID controllers. If the controllers are the same then it's possible they'll just work, but there's no guarantee. Also the type of controller will determine if you can take one disk, plug it into any generic disk controller and have it work (which is only applicable with mirroring anyway).

Cant say I've ever done it myself. Best guess - I've rarely see controllers that store RAID information somewhere on the card (ie, the configuration is on the disks somewhere), so I'd imagine you'd need to plug at least one disk into either identical or compatible cards.

If it were me I'd be looking to move the data to somewhere in the middle first - an external disk or something.

Desmo · 10-01-2008, 12:49

Aye, I've already got an external drive with the jobs backed up. I guess it's just a case of suck it and see :/

Daz · 10-01-2008, 12:49

Do it with 1 drive first. If it fudges up you can always put it back in the first box and restore the mirror.

Mark · 10-01-2008, 13:02

Mirrored? If it's RAID-1, this is the approach I'd use - done this before so I have no reason to doubt it.

1) Backup! I take no responsibility for data loss.

2) If you didn't back up the drive in #1, plug one drive into another system and back it up now. If you can't do this, keep one of the disks back and get a new disk to use as the mirror.
3) Plug one drive into the destination system and see what the controller makes of it. It'll either think it's a single disk or part of a failed RAID-1 array. If it detects as RAID-1, remove the array using whatever tools the controller offers.
4) Remove the disk used in step #3 and plug in the other disk. Repeat the same process. Wipe this disk clean (optional, but recommended to at least remove partitions). Alternatively you can use a non-RAID system and use a tool like dd to erase the whole surface - this will usually obliterate the RAID data as well, but is very slow.
5) Put the disk with data back in the system and re-mirror from this disk to the one you cleaned. Take care to mirror in the right direction!

10-01-2008, 12:46	#2
Daz The Stig Join Date: Jun 2006 Location: Swad! Posts: 10,713	RAID only protects you from disk failure (ie, availability), certainly with a the more complicated RAID types it doesn't save your data from server failure, or at least, it's not guaranteed to. Short answer is it depends on the RAID controllers. If the controllers are the same then it's possible they'll just work, but there's no guarantee. Also the type of controller will determine if you can take one disk, plug it into any generic disk controller and have it work (which is only applicable with mirroring anyway). Cant say I've ever done it myself. Best guess - I've rarely see controllers that store RAID information somewhere on the card (ie, the configuration is on the disks somewhere), so I'd imagine you'd need to plug at least one disk into either identical or compatible cards. If it were me I'd be looking to move the data to somewhere in the middle first - an external disk or something. __________________ apt-get moo

10-01-2008, 12:49	#4
Daz The Stig Join Date: Jun 2006 Location: Swad! Posts: 10,713	Do it with 1 drive first. If it fudges up you can always put it back in the first box and restore the mirror. __________________ apt-get moo

10-01-2008, 12:38	#1
Desmo The Last Airbender Join Date: Jun 2006 Location: Pigmopad Posts: 11,915	Moving RAID set - Help please Seeing as I'm having problems with one of the Macs here (which happens to be the main file server for jobs) I'm looking at moving the jobs discs to another machine. I'm also thinking of possibly putting them onto a spare PC I have. Now, in the Mac I currently have two drives that are RAID mirrored. If I move them to the PC, will they just work? Even if I just use one drive to start with, does that have all the info? Or is it because they're mirrored, they still need to be in a pair? Although that sounds daft as their wouldn't be any point in mirroring if you couldn't recover from one working drive. Also, can you tell that I don't really know what I'm talking about when it comes to RAID stuff? __________________

10-01-2008, 13:02	#5
Mark Screaming Orgasm Join Date: Jul 2006 Location: Newbury Posts: 15,194	Mirrored? If it's RAID-1, this is the approach I'd use - done this before so I have no reason to doubt it. 1) Backup! I take no responsibility for data loss. 2) If you didn't back up the drive in #1, plug one drive into another system and back it up now. If you can't do this, keep one of the disks back and get a new disk to use as the mirror. 3) Plug one drive into the destination system and see what the controller makes of it. It'll either think it's a single disk or part of a failed RAID-1 array. If it detects as RAID-1, remove the array using whatever tools the controller offers. 4) Remove the disk used in step #3 and plug in the other disk. Repeat the same process. Wipe this disk clean (optional, but recommended to at least remove partitions). Alternatively you can use a non-RAID system and use a tool like dd to erase the whole surface - this will usually obliterate the RAID data as well, but is very slow. 5) Put the disk with data back in the system and re-mirror from this disk to the one you cleaned. Take care to mirror in the right direction!