I saw this problem on the cyrus-imap mailing list. Thought I would pass on the information
attached mail follows:
Problem solved!
"sysctl -w net.inet.tcp.delayed_ack=0" solves problem for IMAP and also Postfix, so mainly fsync() was no issue. I had no time to searh why this so drastically affects performance, but maybe somebody will know the answer.
-----Sākotnējā ziņa-----
No: "Juris Orlovs" <jollyroger_at_one.lv>
Sūtīts: 2006-02-09 12:26:13.68
Kam: "info-cyrus_at_lists.andrew.cmu.edu" <info-cyrus_at_lists.andrew.cmu.edu>
Par: slow IMAP data transfer
Hello
I'm trying to set up Cyrus IMAP on freebsd 6.0, but i have problems with performance of it. There is a big issue with message writing to IMAP folders and also with reading a large quantities of messages. Reading of 8MB message takes a bit less than a second, but in that time 8MB message write to IMAP folder over 100Mbit/s connection takes ~6 seconds longer. Also, as I am only one by now who uses this server there could be no chance of big resouce utilization.
Reading/writing ~650 messages, each 1KB) from/to imap folder sends huge amounts of data to RAID 1 arrays. It can be seen using an iostat in that process.
Hardware (2x 3GHx Xeon, 2GB RAM, Adaptec 2410SA,
2x WD RAPTOR 74GB (aacd0)(system), 2x SEAGATE 300GB (aacd1)(mail storage))
Before that I was setting up Cyrus IMAP mail servers on Linux and there was no such problems. Maybe it's OS issue? I also have set up such system on Celeron 800MHz, 256MB RAM and 80GB SEAGATE (FreeBSD 4.11), the results are aproximately the same.
For SMTP i'm using Postfix, and it also shows bad results on data transfer. Seems that the biggest problems I have with mail software, because other services like FTP doesn't show such bad results.
--------------------------------------------------------------------
READING 650 messages
--------------------------------------------------------------------
mx# iostat -Iw 3
tty aacd0 aacd1 cpu
tin tout KB/t xfrs MB KB/t xfrs MB us ni sy in id
0 50 17.54 390334 6687.51 22.46 296070 6492.93 0 0 0 0 100
0 64 16.00 41 0.64 16.00 1 0.02 0 0 0 0 100
0 20 13.00 8 0.10 0.00 0 0.00 1 0 0 0 99
0 20 0.00 0 0.00 0.00 0 0.00 0 0 0 0 100
0 20 13.78 130 1.75 14.67 117 1.68 0 0 1 1 98
0 20 14.64 171 2.45 14.67 120 1.72 0 0 0 0 99
0 20 10.18 201 2.00 14.66 131 1.88 0 0 2 1 98
0 20 12.02 185 2.17 15.25 134 2.00 0 0 1 0 99
0 20 14.23 179 2.49 15.85 135 2.09 0 0 0 0 99
0 20 12.28 215 2.58 16.00 132 2.06 0 0 1 0 99
0 20 10.82 196 2.07 16.00 133 2.08 0 0 1 0 99
0 20 12.80 183 2.29 16.00 135 2.11 0 0 1 0 99
0 20 15.10 178 2.62 16.00 133 2.08 0 0 1 0 99
0 20 10.53 205 2.11 16.00 132 2.06 0 0 1 0 99
0 20 11.19 178 1.95 16.00 132 2.06 0 0 1 0 99
0 20 13.61 179 2.38 16.00 132 2.06 0 0 1 1 99
0 20 13.85 195 2.64 16.00 135 2.11 0 0 1 0 98
0 20 10.07 189 1.86 16.00 133 2.08 0 0 1 0 98
--------------------------------------------------------------------
--------------------------------------------------------------------
WRITING 650 messages
--------------------------------------------------------------------
mx# iostat -Iw 3
tty aacd0 aacd1 cpu
tin tout KB/t xfrs MB KB/t xfrs MB us ni sy in id
0 50 17.50 393390 6724.61 22.40 298277 6526.03 0 0 0 0 100
0 64 9.00 100 0.88 12.90 309 3.89 0 0 0 0 99
0 20 9.00 100 0.88 13.03 303 3.86 0 0 1 0 99
0 20 9.28 100 0.91 12.49 304 3.71 0 0 1 0 99
0 20 9.00 100 0.88 11.99 305 3.57 0 0 1 0 98
0 20 9.00 100 0.88 12.23 310 3.70 1 0 1 0 99
0 20 9.00 100 0.88 12.43 312 3.79 0 0 1 0 99
0 20 8.66 109 0.92 12.60 309 3.80 0 0 0 0 99
0 20 9.00 100 0.88 12.72 305 3.79 0 0 1 0 98
0 20 10.35 124 1.25 12.96 315 3.99 0 0 0 0 99
0 20 9.00 100 0.88 13.18 310 3.99 0 0 1 0 99
0 20 9.00 96 0.84 13.25 299 3.87 0 0 0 0 99
0 20 9.33 105 0.96 13.42 309 4.05 0 0 0 0 99
0 20 9.00 100 0.88 13.41 309 4.05 0 0 1 0 99
0 20 9.00 100 0.88 13.40 308 4.03 0 0 0 0 99
0 20 9.00 100 0.88 13.43 309 4.05 0 0 1 0 99
0 20 9.00 100 0.88 13.52 311 4.11 0 0 1 0 99
0 20 8.83 103 0.89 13.56 308 4.08 1 0 1 0 99
0 20 9.00 100 0.88 13.60 301 4.00 0 0 1 0 99
0 20 9.00 96 0.84 13.56 306 4.05 0 0 1 0 99
--------------------------------------------------------------------
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----
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Received on Wed Feb 15 2006 - 02:46:13 UTC
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