Are blob filenames allocated sequentially based on what is in the message store directory already or by a counter somewhere?
I have moved 7.2.0 from an old to a new server in three phases,
1) Move all of /opt/zimbra when old mail server is still running
2) Stop old server and rsync everything except the message store
3) Start new server and run rsync for the blob store to catch up
This is to reduce downtime when both servers have to be offline.
The concern is that new mail arriving before the blob store rsync in step (3) is complete may be re-allocated blobs already allocated between step (1) and (2).