Re: URGENT: Need help rebuilding iir RAID5 array with failed drive

On Fri, Jun 27, 2008 at 3:05 PM, Derek Ragona
<derek@xxxxxxxxxxxxxxxxxxxxxxxx> wrote:
At 10:04 PM 6/26/2008, Garrett Cooper wrote:

On Thu, Jun 26, 2008 at 8:44 AM, Benjamin Close
<Benjamin.Close@xxxxxxxxxxxxxx> wrote:
Tom Evans wrote:

On Thu, 2008-06-26 at 06:49 -0700, Garrett Cooper wrote:


Hello,
First off sorry for the cross-post. I typically don't do this
but this is an important question, so please bear with me. I'm just
trying to get more eyes on the subject so I can (maybe) get a reply
quicker...
I'm running 8-CURRENT on my machine and it appears that one of
the disks in my RAID5 array has taken a nose dive (BIOS recognizes
that it exists, but Intel Matrix Manager claims that the disk is an
"Offline Member"). After doing some reading it appears that it's
kaput, so I need to get a replacement disk to fix this one...
That aside, I need to determine how to rebuild the array in a
Unix environment because Intel only provides instructions for how to
use their Windows matrix manager. If anyone can point me to some links
or provide me with some pointers on how to correct this issue, I'd owe
you a lot; in fact the next time you come by Santa Cruz, CA I'll
gladly treat you to some beers or something else you might want :)...
Linux solutions (if there isn't a proper one for FreeBSD) are valid,
as long as the core data remains uncorrupted and I can do what I need
to from a LiveCD. I'm just scared to boot up OS and have it do some
irrevocable operation like fsck -y and assume parity errors are ok or
something along those lines (I don't remember if I set rc.conf to
fsck -y and I know I can change that from single-user mode, but I want
to play things conservatively if at all possible) :\...
Filesystem is UFS2 with softupdates of course.
Point proven that I need to backup my data more often :(...
TIA,
-Garrett

PS If replying on the questions@ list, please CC me as I'm not
subscribed to that list.


I'm fairly sure that Intel Matrix metadata cant be created/modified by
fbsd, only read. You should be able to do whatever rebuild operations
you need in the BIOS I believe, but that would be an offline operation,
clearly.

I may be mistaken, and the driver can handle array rebuilds for matrix.
If it can, the command you are looking for is 'atacontrol rebuild ar0',
see atacontrol(8).

Tom


Please DONT use FreeBSD to rebuild this RAID5 unit. FreeBSD will detect it
as a raid 5 Unit and even allow you to use it, add the new disk to it and
even let you rebuild the raid.
However the ata driver does not have support parity for Raid5. From
ataraid(4):

RAID5 is not supported at this time. Code exists, but it neither uses
nor maintains parity information.

You can confirm this in code, just look for the Swedish comments in
ataraid.c
Hence writing to the raidset will give you a glorified raid0.

Cheers,
Benjamin

So.. wait a sec? Are you saying I'm fscked because my RAID5 is nothing
more than RAID0 under FreeBSD?!?!
-Garrett

Most if these RAID's are done in the BIOS so the OS sees just a volume. The
RAID 5 or RAID 1, or RAID 0, or various combinations are left to the BIOS.

Also these are considered software RAIDS not hardware as the BIOS uses the
Motherboard CPU.

-Derek

Grabbed a 1TB drive on sale just for kicks to see if I could rebuild
the array, but I don't see any option at all under FreeBSD (sadly
enough).

So, if I did the following when I setup the RAID, I'm essentially
screwed, aren't I?

1. Configure RAID in Matrix manager.
2. Boot into FreeBSD.
3. Note new device called /dev/ar0.
4. newfs ... /dev/ar0 # Does this mean I did this with RAID0?

-Garrett
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