On Mon, March 2, 2009 1:23 pm, Daniel Pittman wrote:

John Robinson [off-list ref] writes:

quoted

On 01/03/2009 08:52, Daniel Pittman wrote:

quoted

I have a random desktop machine here, running Debian/sid with a 2.6.26
Debian kernel.  It has a two disk software RAID1, and apparently passes
through a suspend/resume cycle correctly, but...

I'm not sure if this is the same suspend/resume - there are after all
several
Googleable reasons why one might suspend or resume various things - but
it
might be worth a look at NeilB's recent post of a patch to "hopefully
enable
suspend/resume of md devices":
http://marc.info/?l=linux-raid&m=123440845819870&w=2

No, that appears to be about suspending and resuming access to the
MD device while reconfiguring it; I don't /think/ that is accessed
during a system-wide suspend/resume (aka hibernate, or s2disk) cycle.

Certainly, it doesn't look like the path is invoked for that from my
reading of the code.

Correct, they are completely unrelated.

I have never tried hibernating to an md array, but I think others have,
though I don't have a lot of specifics.

One observation is that you really don't want resync to start before the
resume has completed.
For this reason we have the  'start_ro' parameter.
Setting that to 1, e.g

  echo 1 > /sys/module/md_mod/parameters/start_ro

will mean that resync will not start until the first write to the array.
The initrd should set this before assembling an md array to load
a resume image from.

If it doesn't, it shouldn't cause major problems, but I'm not making
an promises.

It should be that your observed symtpom of "check reports 48800
mismatches" has nothing to do with hibernate/resume.

Presumably you have swap on md/raid1 (as that is where hibenate writes).
The nature of swap writeout is that it is entirely possible for different
data to be written to each device of a raid1 when a page is swapped out.
However in that case, the data will never be read back in so the
apparent corruption is not a problem.

I would recommend that you run 'repair' before hibernating, to be sure that
the array is in-sync.  Then hibenate/resume and see if it is still in
sync.  I suspect it will be.

NeilBrown