I've put 3 out of the 4 disks of the RAID5 array into a linux PC and
have done:
[root@masterbackend root]# mdadm --assemble /dev/md0 /dev/hde1 /dev/hdf1
/dev/hdg1
mdadm: /dev/md0 has been started with 3 drives (out of 4).
[root@masterbackend root]# more /proc/mdstat
Personalities : [raid5]
read_ahead 1024 sectors
md0 : active raid5 hde1[0] hdg1[2] hdf1[1]
872738880 blocks level 5, 32k chunk, algorithm 2 [4/3] [UUU_]
unused devices: <none>
[root@masterbackend root]# mdadm --detail /dev/md0
/dev/md0:
Version : 00.90.00
Creation Time : Fri May 28 19:09:21 2004
Raid Level : raid5
Array Size : 872738880 (832.31 GiB 893.68 GB)
Device Size : 290912960 (277.44 GiB 297.89 GB)
Raid Devices : 4
Total Devices : 3
Preferred Minor : 0
Persistence : Superblock is persistent
Update Time : Fri May 28 19:37:59 2004
State : dirty, no-errors
Active Devices : 3
Working Devices : 3
Failed Devices : 0
Spare Devices : 0
Layout : left-symmetric
Chunk Size : 32K
Number Major Minor RaidDevice State
0 33 1 0 active sync /dev/hde1
1 33 65 1 active sync /dev/hdf1
2 34 1 2 active sync /dev/hdg1
3 0 0 3 faulty removed
UUID : 3d673dbc:9d78693a:d8ffca9d:d63912cc
Events : 0.5
[root@masterbackend root]# fsck -N /dev/md0
fsck 1.34 (25-Jul-2003)
[/sbin/fsck.ext2 (1) -- /dev/md0] fsck.ext2 /dev/md0
[root@masterbackend root]# mkdir /mnt/array
[root@masterbackend root]# mount /dev/md0 /mnt/array
mount: you must specify the filesystem type
[root@masterbackend root]# mount /dev/md0 /mnt/array -t ext2
mount: wrong fs type, bad option, bad superblock on /dev/md0,
or too many mounted file systems
[root@masterbackend root]# mount /dev/md0 /mnt/array -t jfs
mount: wrong fs type, bad option, bad superblock on /dev/md0,
or too many mounted file systems
[root@masterbackend root]# mount /dev/md0 /mnt/array -t xfs
mount: wrong fs type, bad option, bad superblock on /dev/md0,
or too many mounted file systems
[root@masterbackend root]# mount /dev/md0 /mnt/array -t ext3
mount: wrong fs type, bad option, bad superblock on /dev/md0,
or too many mounted file systems
Am I doing something wrong regarding mounting /dev/md0? I believe the
filesystem used is supposed to be JFS, but I can't seem to mount it as
jfs,xfs,ext2, or ext3. Is there some way I can determine what FS is
used? Could it be a different version of jfs?
Thanks for any help... I believe I'm close!
Tim
> -----Original Message-----
> From: linux-raid-owner@xxxxxxxxxxxxxxx [mailto:linux-raid-
> owner@xxxxxxxxxxxxxxx] On Behalf Of Neil Brown
> Sent: Thursday, May 27, 2004 10:36 PM
> To: Tim Harvey
> Cc: linux-raid@xxxxxxxxxxxxxxx
> Subject: RE: Moving a RAID5 array
>
> On Thursday May 27, tharvey@xxxxxxxxxxxxxxxxxx wrote:
> >
> > It looks like I need to do an 'mdadm --assemble' to assemble the
> > previously created array into an active array. But I'm not clear
how to
> > examine the /dev/md0 device to see what partitions are available
(fdisk
> > didn't work in a test... I guess its not compatible with /dev/md0).
> >
>
> /dev/md0 will not have any partitions. It will just have a
> filesystem.
> You could try 'fsck -n /dev/md0' to see if the filesystem is
recognised.
>
> > >
> > > Issue #1 Can be assured (AFAIK) by just attaching one disk less.
Then
> > the
> > > array will be in degraded mode and cannot / will not attempt a
resync.
> > > In addition, this will enable you to choose another set of disks,
> > should
> > > the
> > > outlook on the first three be less than favourable...
> > >
> >
> > Does disallowing the raid to start any reconstruction mean that the
> > array is not 'started' and that I cannot mount the filesystem? I
guess
> > I'm not clear if there is a difference between the array being
'started'
> > and 'allowing reconstruction'. Is leaving a disk out of the RAID5
array
> > the only way to force this to occur? I noticed mdadm has a
--readonly
> > option but I'm not sure if it affects the assemble mode.
>
> "starting" an array is like mounting a filesystem. It makes it
> accessible.
> There is no simple way to start an array but not let it
> reconstruct. '--readonly' doesn't do this (though it probably
> should).
> Leaving one drive out disables reconstruction simply by making it
> impossible.
>
> >
> > > Issue #2 Should be assured by mounting read-only, without prior
fsck.
> > >
> >
> > Sounds like a safe bet to mount the partition read-only. How can I
> > examine /dev/md0 to see what partitions are available? I'm fairly
> > certain XFS is used. The RAID HOWTO doesn't seem to go into detail
> > regarding how to examine filesystems on an array.
>
> There are no partition tables. Just a filesystem. Does xfs have a
> check-and-repair tool? Try that.
>
> NeilBrown
> -
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