Re: A little story of failed raid5 (3ware 8000 series)


----- "Artem Kuchin" <matrix@xxxxxxxxxxx> wrote:
...
But i don't understand how and why it happened. ONly 6 hours ago (a
night before)
all those files were backed up fine w/o any read error. And now, right
after replacing
the driver and starting rebuild it said that there are bad sectors all
over those file.
How come?

What happened to you was an extremely common occurrence. You had a disk develop a media failure sometime ago, but the controller never detected it, because that particular bad area was not read. Your backups worked because they never touched this portion of the disk (ex. empty space, meta data, etc). And then another drive developed a electronics failure, which is instantly detected, putting the array into a degraded mode. When you did a rebuild onto a replace drive, the controller discovered that there was a second failed disk, and this is unrecoverable.

RAID, of any level, isn't magic. It is important to understand how it works, an realize that drives can passive fail. BTW, if you were using RAID1 or RAID10, you would likely have had the same problem (well, RAID10 can survive _some_ double-disk failures). RAID6 is the only RAID level that can survive failure of any two disks.

The real solution is RAID scrubbing: a low level background process that reads every sector of every disk. All of the real RAID systems do this (usually scheduled weekly, or every other week). Most 3ware RAID card don't have this feature.

So rather than not using RAID5 or RAID6 again, you should just not use 3ware anymore.


Tom
_______________________________________________
freebsd-stable@xxxxxxxxxxx mailing list
http://lists.freebsd.org/mailman/listinfo/freebsd-stable
To unsubscribe, send any mail to "freebsd-stable-unsubscribe@xxxxxxxxxxx"

Relevant Pages

  • rebuild problems with ata-raid on array with freebsd native meta
    ... First of all i have a intel se7520jr2 motherboard with SATA RAID ... by creating RAID1 array in LSI Integrated RAID ... but `atacontrol rebuild ar0` always had had ENXIO ...
    (freebsd-current)
  • Re: SiI RAID 1 Problems: "You can not rebuild"
    ... Used Maxtor Power Max utility to scan for errors on my hard drives. ... Rebooted and entered the RAID utility. ... Create a new mirrored set, ... I then perform an online rebuild (which runs in the ...
    (microsoft.public.windowsxp.general)
  • Re: Bad RAID Configuration Need Rebuild 1st DC
    ... I'm told that there is a bad strip any attempts to rebuild fail even though ... So I'm looking for the best solution to backup and restore this DC! ... > I understand you one stripe is broken in the OS RAID 1 on one of your DCs. ...
    (microsoft.public.windows.server.setup)
  • Re: Asus P5Q-E
    ... When I reboot I saw the raid volume 0 being labelled in yellow as Rebuild. ... Today I found the driver associated with the volume 0 as Microsoft. ... If a shutdown is happening, there is a difference between a controlled ...
    (alt.comp.periphs.mainboard.asus)
  • Re: URGENT: Need help rebuilding iir RAID5 array with failed drive
    ... You should be able to do whatever rebuild operations ... >> you need in the BIOS I believe, but that would be an offline operation, ... > Please DONT use FreeBSD to rebuild this RAID5 unit. ... > even let you rebuild the raid. ...
    (freebsd-current)