Re: [PATCH 0/9] recovering an imsm raid5 array

[NeilBrown <neilb@suse.de>]

On Thu, 25 Aug 2011 19:13:59 -0700 Dan Williams <dan.j.williams@intel.com>
wrote:

> I run imsm raid5 and raid1 arrays on my personal systems and was
> recently bit by the bug that was fixed in commit 1a2487c2 "FIX: imsm:
> OROM does not recognize degraded arrays (V2)".  In the process of
> investigating that I pulled the wrong disk and ended up in a dual
> degraded situation.
> 
> These patches (ordered in roughly increasing order of required review)
> are the features needed to get the array up and running again, as well
> as some random fixes spotted along the way.
> 
> The most important patch for recovery being patch7 "imsm: support
> 'missing' devices at Create", allowing the mdadm raid5 recovery path of
> recreating the raid array with what one thinks are the good disks /
> order, and then  attempt to mount the filesystem to see if the guess was
> correct.
> 
> Example, create degraded raid5 with slot1 missing.
> 
> mdadm --create /dev/md0 /dev/sd[ac] -n 2 -e imsm
> mdadm --create /dev/md1 /dev/sda missing /dev/sdc -n 3 -l 5
> 
> However, during this process I wanted to make sure I could get back to
> the exact same metadata that was on the disks, to root cause what went
> wrong, examine the metadata offline, or backup a step if I made a
> mistake in the recovery process.  Patch9 implements --dump support, the
> fact that something like this has not been implemented already is maybe
> a clue that it is not such a great idea?  I can imagine someone messing
> up their configuration if they restored a metadata image to the wrong
> device, but if you know what you are doing it could be a useful hack.
> 
> ---
> 
> Dan Williams (9):
>       imsm: fix max disks per array
>       imsm: fix, stop metadata updates to newly failed devices
>       imsm: fix display spares
>       sysfs: fix sysfs_disk_to_scsi_id
>       imsm: fix reserved sectors for spares
>       mdmon: fix, close spare activation race
>       imsm: support 'missing' devices at Create
>       util: allow regular files through test_partition()
>       mdadm: 'dump' support
> 
> 
>  Examine.c     |   42 ++++++++++++++++
>  ReadMe.c      |    1 
>  managemon.c   |    5 ++
>  mdadm.8.in    |   13 +++++
>  mdadm.c       |   11 ++++
>  mdadm.h       |    3 +
>  super-intel.c |  146 +++++++++++++++++++++++++++++++++++++--------------------
>  sysfs.c       |   30 ++++--------
>  util.c        |    6 ++
>  9 files changed, 182 insertions(+), 75 deletions(-)

Thanks.
I've applied all but the last two - which I might want done slightly
differently as discussed already.

I also fixed a build breakage in "make everything" .... though maybe I should
get rid of mdassemble - it is hard to maintain and I'm not really sure that
it is useful.

Thanks,
NeilBrown