Now that I have a working kvm setup, I thought I'd finally try how Zimbra works. This is mainly some microbenchmarking, so it may not have much to do with actual performance in real life.
Setup:
- 1GB memory given to kvm (from host's 2GB)
- Intel Core 2 6600 (kvm uses only one CPU)
- CentOS 5
- 15GB qcow2 image on XFS filesystem
- Zimbra 5.0 RC2 RHEL5 x86_64
- Dovecot latest hg, dbox format
Both Zimbra and Dovecot were tested running on the same kvm image. All data could be cached in memory, so this didn't really test disk I/O.
Dovecot was run with fsync_disable=no. Running with =yes would have made its performance even better.
Zimbra features/bugs
Zimbra's SEARCH command doesn't support substring searching as IMAP requires:
1 search text performance
- SEARCH 136 183 227 231 232 233 245 1 OK SEARCH completed 2 search text erformance
- SEARCH 2 OK SEARCH completed 3 search text performanc
- SEARCH 3 OK SEARCH completed
It's possible to search "performanc" in a non-standard way though:
4 search text "performanc*"
- SEARCH 136 183 227 231 232 233 245 4 OK SEARCH completed
This means that the upcoming Dovecot v1.1 is probably the only IMAP server that supports IMAP-compatible full text search indexes with incremental updates. (Cyrus Squat requires rebuilding the whole index from scratch just for adding one mail, which makes it kind of impractical.)
Zimbra doesn't support SORT or THREAD extensions.
I had trouble benchmarking more than 5 simultaneous connections in one mailbox. I'm not sure if this is a configurable setting somewhere, or if there's just some bug. The error messages that my imaptest gave looked like Zimbra was buggy, but I didn't look at them too closely.
STORE command also seemed to be buggy, giving lots of "STORE failed" errors, even with just one connection.
Zimbra uses 500MB of memory just to start up, so it's not exactly for hosting small installations.
Login+Logout
Dovecot:
./imaptest - select=0 secs=10 seed=0 clients=1 Logi Logo 100% 100% 3439 6878 ./imaptest - select=0 secs=10 seed=0 clients=10 Logi Logo 100% 100% 4415 8830
Zimbra:
./imaptest - select=0 secs=10 seed=0 clients=1 Logi Logo 100% 100% 18032 36064 ./imaptest - select=0 secs=10 seed=0 clients=10 Logi Logo 100% 100% 25519 51056
Looks like Dovecot's imap process creation hurts it a lot compared to Zimbra's thread creation. Luckily IMAP connections are usually long-living, so this shouldn't matter much, except for webmails for which you can use imapproxy in the middle.
LIST "" *
Dovecot:
./imaptest - select=0 logout=0 list=100 secs=10 seed=0 clients=1 Logi List 100% 100% 1 181411 ./imaptest - select=0 logout=0 list=100 secs=10 seed=0 clients=10 Logi List 100% 100% 10 133451
Zimbra:
./imaptest - select=0 logout=0 list=100 secs=10 seed=0 clients=1 Logi List 100% 100% 1 1021 ./imaptest - select=0 logout=0 list=100 secs=10 seed=0 clients=10 Logi List 100% 100% 10 972
Yes, Dovecot's LIST is over 100 times faster.
STATUS INBOX (MESSAGES UNSEEN RECENT)
100 messages in INBOX
dovecot:
./imaptest - logout=0 select=0 status=100 secs=10 seed=0 clients=1 Logi Stat 100% 100% 1 191003 ./imaptest - logout=0 select=0 status=100 secs=10 seed=0 clients=10 Logi Stat 100% 100% 10 171171
Zimbra:
./imaptest - logout=0 select=0 status=100 secs=10 seed=0 clients=1 Logi Stat 100% 100% 1 3697 ./imaptest - logout=0 select=0 status=100 secs=10 seed=0 clients=10 Logi Stat 100% 100% 10 7009
FETCH 1:* (UID FLAGS ENVELOPE INTERNALDATE BODYSTRUCTURE)
100 messages in INBOX.
dovecot: ./imaptest - logout=0 select=100 fetch=100 secs=10 seed=0 clients=1 Logi Sele Fetc 100% 100% 100% 1 1 2769 ./imaptest - logout=0 select=100 fetch=100 secs=10 seed=0 clients=5 Logi Sele Fetc 100% 100% 100% 5 5 2902
Zimbra:
./imaptest - logout=0 select=100 fetch=100 secs=10 seed=0 clients=1 Logi Sele Fetc 100% 100% 100% 1 1 203 ./imaptest - logout=0 select=100 fetch=100 secs=10 seed=0 clients=5 Logi Sele Fetc 100% 100% 100% 5 5 258
FETCH ? (BODY[])
Randomly fetch message body from 100 messages
Dovecot:
./imaptest - logout=0 select=100 fetch2=100 secs=10 seed=0 clients=1 Logi Sele Fet2 100% 100% 100% 30% 1 1 51958 ./imaptest - logout=0 select=100 fetch2=100 secs=10 seed=0 clients=5 Logi Sele Fet2 100% 100% 100% 30% 5 5 141397
Zimbra:
./imaptest - logout=0 select=100 fetch2=100 secs=10 seed=0 clients=1 Logi Sele Fet2 100% 100% 100% 30% 1 1 410 ./imaptest - logout=0 select=100 fetch2=100 secs=10 seed=0 clients=5 Logi Sele Fet2 100% 100% 100% 30% 5 5 2291
STORE ? FLAGS.SILENT (random flags and keywords)
Dovecot:
./imaptest - logout=0 select=100 store=100 secs=10 seed=0 clients=1 Logi Sele Stor 100% 100% 100% 1 1 15236 ./imaptest - logout=0 select=100 store=100 secs=10 seed=0 clients=5 Logi Sele Stor 100% 100% 100% 5 5 5533
Zimbra:
./imaptest - logout=0 select=100 store=100 secs=10 seed=0 clients=1 Logi Sele Stor 100% 100% 100% 1 1 308 ./imaptest - logout=0 select=100 store=100 secs=10 seed=0 clients=5 Logi Sele Stor 100% 100% 100% 5 5 319
Zimbra gave lots of errors: Error: STORE failed: STORE failed
APPEND
Appends to empty mailbox:
Dovecot: 1 client, 5 seconds: 3959 mails 1 client, 5 seconds, fsync_disable=yes: 21889 mails
Zimbra: 1 clients, 5 seconds: 222 mails 5 clients, 5 seconds: 322 mails
Zimbra is apparently building full text search indexes while appending, so this test doesn't mean much until I can test Dovecot's performance with Squat indexing.