sync prob with big files

[fuzzy_4711]

Hi list.

We have 2 NAS-Devices, each mounted on the same (virtual) box. For our
backup we use bacula. Bacula ist writing its files to the first NAS
(192.168.1.9). These are big files, up to 160 GB.

For implementing a good backup strategy we decided to mirror (sync)
another NAS-Device (192.168.1.8) to have redundant bacula backups. If
sync is done the Device will be kept at another location too.

I do have problems with syncing. rsync is exiting with error-code 1.
Sometimes early, sometimes late in progress. This is what I am using in
a shell script:

rsync --omit-dir-times --size-only -avzAX \
--bwlimit=$KILOBYTES_PER_SECOND --devices --specials --numeric-ids \
--delete $BACULA_BACKUP_DIR $MOUNT_DIR/$SYNC_DIR

The bandwidth limit is 2500 kps. Without the limit it was working so far
since my boss told me to stop using it this way because he was afraid of
rsync taking all the network resources.

BTW, both NAS-Devices are mounted aus type cifs. My rsync version is
rsync  version 3.0.7  protocol version 30

Is this a known issue or does this make sense to anyone in any way?

Thanks for your help.
-fuz