[OpenAFS] file corruption after restoring large readonly volumes

[Jeffrey Hutzelman]

On Tuesday, August 24, 2004 19:17:15 -0700 Brendan Kirby 
<bkirby@mvista.com> wrote:

> Drive to remote location, hook up the drive to the other machine, then:
> vos restore -server remote-server -partition /vicepb -name vol -id
> vol.readonly -readonly -overwrite full < /path/to/disk/dumpfile vos
> release vol

This will not work, because 'vos restore -readonly' does not currently 
create volumes which are suitable targets for later releases. 
Particularly, it does not set the volume last-update timestamp correctly, 
nor does it set the parent volume ID's on vnodes in the new volume.


The first problem means that a later vos release will use an incremental 
dump with an incorrect (too late) start time.  The result is that the RO 
volume after the release may contain old contents for some files and 
directories, and may contain directory entries for files whose contents are 
not in the volume at all.

This problem can be worked around using new functionality provided by DELTA 
volser-restore-timestamp-cleanup-20040728, which first appeared in OpenAFS 
1.3.70.  This delta adds the -creation and -lastupdate switches to vos 
restore, which control how the timestamps are generated:

  vos restore ... -readonly -lastupdate dump

For this to work, you must be using the new vos, and the target server must 
be running the new volserver which supports this feature.


The second problem will be completely fatal on namei platforms (such as 
Linux) if you ever try to move the RW volume to the site where you did the 
manual restore.  If you don't plan on ever doing that, I believe doing the 
restore is safe, but I don't have a whole lot of operational experience 
with the namei fileserver.  Perhaps someone else who has investigated this 
issue more completely will comment...


-- Jeffrey T. Hutzelman (N3NHS) <jhutz+@cmu.edu>
   Sr. Research Systems Programmer
   School of Computer Science - Research Computing Facility
   Carnegie Mellon University - Pittsburgh, PA