[OpenAFS] Strange sizes of incremental volume dumps

[Friedrich Delgado Friedrichs]

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Hi.

On an OpenAFS Installation here we're doing nightly volume backups
with vos backupsys at 0:30 and the backup volumes are dumped during
the day with vos dump.

There's a monthly level 0 backup without a timestamp, done with

/usr/sbin/vos dump -id root.afs.backup -local

And after that incremental dumps are run with e.g.:

/usr/sbin/vos dump -id root.afs.backup -time 03/09/2009 00:30 -local

i.e. in this case the level 0 dump was done on the 9th march 2009.

Today we noticed that the size of the incremental dumps is non-zero
for some volumes which have not changed in quite a while.

e.g. we have a volume that hasn't changed in over 2 weeks

vos exa gives the following output for the RW-replica:

,----
       RWrite  536871467 ROnly          0 Backup  536871469
       MaxQuota    8388608 K
       Creation    Mon Sep 29 16:48:08 2008
       Copy        Mon Sep 29 16:48:08 2008
       Backup      Wed Mar 11 00:33:03 2009
       Last Update Wed Feb 25 15:25:53 2009
       65453 accesses in the past day (i.e., vnode references)


       RWrite: 536871467     Backup: 536871469
       number of sites -> 1
`----

The incremental dump of that volume is 50MB in size, the level 0 dump
being 4GB.

We found some other volumes that had not changed since March 9th, and
there doesn't seem to be a relation between the size of the full and
incremental dumps.

e.g. we have: 4GB vs. 7.8MB in one case and 1.7GB vs. 172MB in
another.

In one case it was observed that the size of the incremental dump
seems to increase by about one block a day.

Running unpatched 1.4.8 openafs, both client and server running
openSUSE, 11.1 on the server, kernel 2.6.27.7, 10.3 on the clients
with kernel version 2.6.22.19.

Can anybody explain this? Is it a bug, a feature, a configuration
error?

If you need any more information, please feel free to ask!

Kind regards
     Friedel
--=20
Dipl.-Inform. Friedrich Delgado Friedrichs (Projekt- und Entwicklungsteam)
DFN-CERT Services GmbH, https://www.dfn-cert.de,  Phone  +49 40 808077-555
Sitz / Register: Hamburg, AG Hamburg, HRB 88805,  Ust-IdNr.:  DE 232129737
Sachsenstra=DFe 5, 20097 Hamburg/Germany, CEO: Dr. Klaus-Peter Kossakowski

                      16. DFN-Workshop Sicherheit in vernetzten Systemen
                                         https://www.dfn-cert.de/ws2009/

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