On 29.04.2010 21:02, Timo Sirainen wrote:
On Mon, 2010-04-26 at 15:51 +0300, karavelov wrote:
- My understanding is that OCFS2 uses a global lock for move/rename. As you know, Maildir format uses a lot of such operations. I think that dbox format (dovecot native) will be better choice, because there are no file moves/renames. I am planning migration to dbox now. If I have to start the service now, I would choose dbox for mail storage.
Wonder what the performance difference is then between v2.0's single-dbox and multi-dbox? I'd guess mdbox is faster.
Here are some benchmarks that were done with imaptest. The used commands are imaptest host=rhp2 mbox=dovecot.mbox user=test@example.com pass="test" seed=123 secs=10 imaptest host=rhp2 mbox=dovecot.mbox user=test@example.com pass="test" seed=123 secs=10 logout=0
The volume is an iscsi export (4 SATA disks in a stripe) mounted on a imap test server (no other processes are running). On OCFS2 setup, the filesystem is mounted also on another node (2 node test cluster). The other node was also idle.
Here are my results:
Logi List Stat Sele Fetc Fet2 Stor Dele Expu Appe Logo
100% 50% 50% 100% 100% 100% 50% 100% 100% 100% 100%
30% 5%nologout 10 139 130 10 248 350 87 196 248 248 XFS
maildir
logout 227 121 127 227 216 323 60 170 216 221 454 XFS
maildir
nologout 10 733 713 10 1438 2094 467 1161 1438 1438 OCFS2
maildir
logout 584 300 282 584 547 780 170 428 547 580 1168 OCFS2
maildir
nologout 10 930 892 10 1825 2614 527 1489 1825 1825 OCFS2 dbox
logout 570 290 298 569 564 838 226 452 564 568 1140 OCFS2 dbox
DISCLAIMER: Dovecot server is tuned for best performance with OCFS2 as far as I can because my current production setup is OCFS2 based. XFS is included for comparison without much of tuning. Mount options are:
XFS: noatime,nodiratime,logbufs=8,logbsize=131072 OCFS2: noatime,data=writeback,commit=30
I have tested also NFS4 but the results were disappointing so I abandoned further tests because no tuning could make a x10 difference.
My expectation is that pushing dbox in production will have even more gains than my tests show because it will lower internal OCFS2 locking on move and rename.
My tests and benchmarks were done using v1.2.11. May be I should make some benchmarks for mdbox also using dovecot v2. My understanding is that dbox is forward compatible with mdbox and there will be no need to convert mailboxes from dbox to mdbox. Is it that ot there will be another pain in migrationg mailboxes from one format in another?
Best regards luben