Re: BUG:write data to degrade raid5

[Robin Hill <robin@robinhill.me.uk>]

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On Fri Mar 19, 2010 at 07:20:42PM +0100, Joachim Otahal wrote:

> jin zhencheng schrieb:
> > hi;
> >
> > i use kernel is 2.6.26.2
> >
> > what i do as follow:
> >
> > 1, I create a raid5:
> > mdadm -C /dev/md5 -l 5 -n 4 /dev/sda /dev/sdb /dev/sdc  /dev/sdd
> > --metadata=1.0 --assume-clean
> >
> > 2, dd if=/dev/zero of=/dev/md5 bs=1M&
> >
> > write data to this raid5
> >
> > 3, mdadm --manage /dev/md5 -f /dev/sda
> >
> > 4 mdadm --manage  /dev/md5 -f /dev/sdb
> >
> > if i faild 2 disks ,then the OS kernel display OOP error and kernel down
> >
> > do somebody know why ?
> >
> > Is MD/RAID5 bug ?
> >    
> 
> RAID5 can only tolerate ONE drive to fail of ALL members. If you want to 
> be able to fail two drives you will have to use RAID6 or RAID5 with one 
> hot-spare (and give it time to rebuild before failing the second drive).
> PLEASE read the documentation on raid levels, like on wikipedia.
> 
Yes, but the kernel should _not_ OOPS if two drives fail.  However,
given that the kernel version used is 18 months old, I'm not sure the
bug report is particularly useful.  If it's a distro-specific kernel
then report the issue to them, otherwise try installing a more recent
kernel release.

Cheers,
    Robin
-- 
     ___        
    ( ' }     |       Robin Hill        <robin@robinhill.me.uk> |
   / / )      | Little Jim says ....                            |
  // !!       |      "He fallen in de water !!"                 |

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