Hi all,
We are currently using snapshots and rsync to backup a large
mail server to a backup mail server. I have been looking into using
dsync to replace rsync in hopes that it would make backups more
efficient. I decided to test the performance using a single mailbox.
Unfortunately dsync seems to run much slower than rsync. Rsync was able
to sync the mailbox in 2 seconds. dsync took over a minute. The test was
run so that the source and destination are on the same filesystem.
We would like to using the new replication system, but that
doesn't seem likely since the performance of the underlying dsync is so
much slower than rsync. Even with the extra work that dsync is doing I
can't believe the difference in performance would be that great. I
realize that dsync is actively being worked on and I hope bringing
attention to performance issue will provoke some ideas on how to improve
it.
Here is the output of the tests using dovecot 2.1.3:
[root at n24 bu]# du -hs /home/10.0.1.101/1009/users/testuser%
domain.com/Maildir/
517M /home/10.0.1.101/1009/users/testuser%domain.com/Maildir/
[root at n24 bu]# time rsync -va /home/10.0.1.101/1009/users/testuser%
domain.com/Maildir/ .
sending incremental file list
Maildir/
Maildir/dovecot-uidlist
[ ... deleted cruft ... ]
Maildir/cur/1332387577.M381054P27635.n24,S=14215502,W=14448554:2,
Maildir/new/
Maildir/tmp/
sent 540927820 bytes received 1222 bytes 216371616.80 bytes/sec
total size is 540855755 speedup is 1.00
real 0m2.677s
user 0m3.184s
sys 0m1.513s
[root at n24 bu]# time dsync backup -u testuser at domain.com \
mdbox:/home/bu/testuser
real 1m9.519s
user 1m7.592s
sys 0m1.126s
[root at n24 bu]# time dsync backup -u testuser at domain.com \
sdbox:/home/bu/testuser2
real 1m2.164s
user 1m0.882s
sys 0m0.993s
[root at n24 bu]#