URGENT: Need help rebuilding iir RAID5 array with failed drive

[Garrett Cooper]

On Thu, Jun 26, 2008 at 8:44 AM, Benjamin Close
<Benjamin.Close at clearchain.com> 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