Re: RAID 0 went down...

Re: RAID 0 went down...

[Mike Tran]

Hi Romeyn,

If there were I/O errors on one of the disks, I am not sure that you
want to re-assemble/re-create this "corrupted" raid0 array.  However, if
you just want to get some data out of the volume /dev/md0, you can use
mdadm to re-create the array:

mdmadm -C -R /dev/md0 -c 64 -l 0 -n 2 /dev/sdb1 /dev/sdc1

Regards,
Mike T.

On Mon, 2004-10-11 at 07:28, Romeyn Prescott wrote:
> I have a RH 9.0 box with a RAID 0.  I started getting some I/O errors
> and when I rebooted the box md0 wouldn't mount.
> 
> /etc/raiddtab:
> -----
> raiddev             /dev/md0
> raid-level                  0
> nr-raid-disks               2
> chunk-size                  64k
> persistent-superblock       1
> nr-spare-disks              0
>     device          /dev/sdb1
>     raid-disk     0
>     device          /dev/sdc1
>     raid-disk     1
> -----
> 
> The problem appears to be with /dev/sdc, yet it passes all of the
> manufacturer's (Seagate) diagnostics.  Here's what /var/log/dmesg
> says:
> -----
> md: Autodetecting RAID arrays.
>  [events: 00000095]
>  [events: 00000031]
> md: autorun ...
> md: considering sdc1 ...
> md:  adding sdc1 ...
> md:  adding sdb1 ...
> md: created md0
> md: bind<sdb1,1>
> md: bind<sdc1,2>
> md: running: <sdc1><sdb1>
> md: sdc1's event counter: 00000031
> md: sdb1's event counter: 00000095
> md: superblock update time inconsistency -- using the most recent one
> md: freshest: sdb1
> md: kicking non-fresh sdc1 from array!
> md: unbind<sdc1,1>
> md: export_rdev(sdc1)
> md0: former device sdc1 is unavailable, removing from array!
> md0: max total readahead window set to 512k
> md0: 2 data-disks, max readahead per data-disk: 256k
> md: md0, array needs 2 disks, has 1, aborting.
> raid0: disks are not ordered, aborting!
> md: pers->run() failed ...
> md :do_md_run() returned -22
> md: md0 stopped.
> md: unbind<sdb1,0>
> md: export_rdev(sdb1)
> md: ... autorun DONE.
> -----
> 
> Is there any way I can recover from this?  I've been googling my
> brains out, but most of what I find relates to RAID1.  Restoring from
> a backup is possible, but..."complicated" and is my last resort.
> 
> TIA,
> ...ROMeyn

RAID 0 went down...

[Romeyn Prescott]

I have a RH 9.0 box with a RAID 0.  I started getting some I/O errors
and when I rebooted the box md0 wouldn't mount.

/etc/raiddtab:
-----
raiddev             /dev/md0
raid-level                  0
nr-raid-disks               2
chunk-size                  64k
persistent-superblock       1
nr-spare-disks              0
    device          /dev/sdb1
    raid-disk     0
    device          /dev/sdc1
    raid-disk     1
-----

The problem appears to be with /dev/sdc, yet it passes all of the
manufacturer's (Seagate) diagnostics.  Here's what /var/log/dmesg
says:
-----
md: Autodetecting RAID arrays.
 [events: 00000095]
 [events: 00000031]
md: autorun ...
md: considering sdc1 ...
md:  adding sdc1 ...
md:  adding sdb1 ...
md: created md0
md: bind<sdb1,1>
md: bind<sdc1,2>
md: running: <sdc1><sdb1>
md: sdc1's event counter: 00000031
md: sdb1's event counter: 00000095
md: superblock update time inconsistency -- using the most recent one
md: freshest: sdb1
md: kicking non-fresh sdc1 from array!
md: unbind<sdc1,1>
md: export_rdev(sdc1)
md0: former device sdc1 is unavailable, removing from array!
md0: max total readahead window set to 512k
md0: 2 data-disks, max readahead per data-disk: 256k
md: md0, array needs 2 disks, has 1, aborting.
raid0: disks are not ordered, aborting!
md: pers->run() failed ...
md :do_md_run() returned -22
md: md0 stopped.
md: unbind<sdb1,0>
md: export_rdev(sdb1)
md: ... autorun DONE.
-----

Is there any way I can recover from this?  I've been googling my
brains out, but most of what I find relates to RAID1.  Restoring from
a backup is possible, but..."complicated" and is my last resort.

TIA,
...ROMeyn

-- 
http://www2.potsdam.edu/prescor/signat-url.htm

Re: RAID 0 went down...

[Romeyn Prescott]

Thanks for the advice.

Actually, after I posted I did some more Googling and discovered
mdadm, which didn't appear to be included with RH 9.0.  I installed it
and was able to use the -A option with the -f (force) command ti get
the RAID back up and mounted.  I have copied just about all of the
data off of it!

As I look over this some more (I'm no RAID expert) it seems to me that
if I could just somehow re-synchronize the "superblock update times"
that md0 would get automatically recreated at boot instead of failing
out.  Is there any way to do that?  When I forced the mount, I checked
the logs and the filesystem has been flagged for an fsck, but that'll
never happen if md0 isn't reconstituted at boot!

TIA,
...ROMeyn


On Mon, 11 Oct 2004 05:10:40 -0500, Mike Tran <mhtran@us.ibm.com> wrote:
> Hi Romeyn,
> 
> If there were I/O errors on one of the disks, I am not sure that you
> want to re-assemble/re-create this "corrupted" raid0 array.  However, if
> you just want to get some data out of the volume /dev/md0, you can use
> mdadm to re-create the array:
> 
> mdmadm -C -R /dev/md0 -c 64 -l 0 -n 2 /dev/sdb1 /dev/sdc1
> 
> Regards,
> Mike T.
> 
> 
> 
> On Mon, 2004-10-11 at 07:28, Romeyn Prescott wrote:
> > I have a RH 9.0 box with a RAID 0.  I started getting some I/O errors
> > and when I rebooted the box md0 wouldn't mount.
> >
> > /etc/raiddtab:
> > -----
> > raiddev             /dev/md0
> > raid-level                  0
> > nr-raid-disks               2
> > chunk-size                  64k
> > persistent-superblock       1
> > nr-spare-disks              0
> >     device          /dev/sdb1
> >     raid-disk     0
> >     device          /dev/sdc1
> >     raid-disk     1
> > -----
> >
> > The problem appears to be with /dev/sdc, yet it passes all of the
> > manufacturer's (Seagate) diagnostics.  Here's what /var/log/dmesg
> > says:
> > -----
> > md: Autodetecting RAID arrays.
> >  [events: 00000095]
> >  [events: 00000031]
> > md: autorun ...
> > md: considering sdc1 ...
> > md:  adding sdc1 ...
> > md:  adding sdb1 ...
> > md: created md0
> > md: bind<sdb1,1>
> > md: bind<sdc1,2>
> > md: running: <sdc1><sdb1>
> > md: sdc1's event counter: 00000031
> > md: sdb1's event counter: 00000095
> > md: superblock update time inconsistency -- using the most recent one
> > md: freshest: sdb1
> > md: kicking non-fresh sdc1 from array!
> > md: unbind<sdc1,1>
> > md: export_rdev(sdc1)
> > md0: former device sdc1 is unavailable, removing from array!
> > md0: max total readahead window set to 512k
> > md0: 2 data-disks, max readahead per data-disk: 256k
> > md: md0, array needs 2 disks, has 1, aborting.
> > raid0: disks are not ordered, aborting!
> > md: pers->run() failed ...
> > md :do_md_run() returned -22
> > md: md0 stopped.
> > md: unbind<sdb1,0>
> > md: export_rdev(sdb1)
> > md: ... autorun DONE.
> > -----
> >
> > Is there any way I can recover from this?  I've been googling my
> > brains out, but most of what I find relates to RAID1.  Restoring from
> > a backup is possible, but..."complicated" and is my last resort.
> >
> > TIA,
> > ...ROMeyn
> 
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-- 
http://www2.potsdam.edu/prescor/signat-url.htm