Re: (Re: Questions regarding startup of imsm container)

[Dan Williams <dan.j.williams@intel.com>]

On Tue, Mar 23, 2010 at 7:33 AM, Randy Terbush <randy@terbush.org> wrote:
> To follow-up this startup challenge... here is what I am getting.
>
> mdraid is being started with mdadm -As
>
> I have the following in mdadm.conf
>
> HOMEHOST Volume0
> #DEVICE /dev/sd[bcde]
> AUTO +imsm hifi:0 -all
> ARRAY metadata=imsm UUID=30223250:76fd248b:50280919:0836b7f0
> ARRAY /dev/md/Volume0 container=30223250:76fd248b:50280919:0836b7f0
> member=0 UUID=8a4ae452:da1e7832:70ecf895:eb58229c
>
> The following devices are being created.
>
> # ls -l /dev/md/
> total 0
> lrwxrwxrwx 1 root root 6 Mar 23 08:10 0 -> ../md0
> lrwxrwxrwx 1 root root 8 Mar 23 08:17 126 -> ../md126
> lrwxrwxrwx 1 root root 8 Mar 23 08:17 127 -> ../md127
> lrwxrwxrwx 1 root root 8 Mar 23 08:17 imsm0 -> ../md127
> lrwxrwxrwx 1 root root 8 Mar 23 08:17 Volume0 -> ../md126
>
> cat /proc/mdstat
> Personalities : [linear] [raid0] [raid1] [raid10] [raid6] [raid5] [raid4]
> md126 : active raid5 sdb[3] sdc[2] sdd[1] sde[0]
>      2930280448 blocks super external:/md127/0 level 5, 64k chunk,
> algorithm 0 [4/4] [UUUU]
>      [>....................]  resync =  1.8% (18285824/976760320)
> finish=182.6min speed=87464K/sec
>
> md127 : inactive sde[3](S) sdb[2](S) sdc[1](S) sdd[0](S)
>      9028 blocks super external:imsm
>
> unused devices: <none>
>
> So the container device is getting moved from md0 to md127. Not sure why.

You didn't specify a device name for it in the configuration file so
mdadm picked one for you.

> And would sure like to have a write-intent bitmap active to avoid this
> resync issue which seems to be happening way too frequently.

This could also be a problem with your distribution not taking care of
mdmon properly at shutdown.  The shutdown scripts need to keep mdmon
alive over the final "remounting rootfs readonly" event and wait for
it to mark the array/metadata clean.  Otherwise there is a good chance
that the array will be left dirty and require a resync at startup.

Also note that recent versions of mdadm (3.1.2) and the kernel
(2.6.33) can checkpoint imsm resyncs so at least it will not start
over from the beginning when you reboot in the middle of a resync.

--
Dan
--
To unsubscribe from this list: send the line "unsubscribe linux-raid" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html