<br>A pictures says a thousand words... Here is the pattern we see lately:<br><br><div><img alt="Inline image 2" src="cid:ii_13c5d718d69c4e3f"><img alt="Inline image 1" src="cid:ii_13c5d7167491a290"><br><br>Green indicates active messages in the postfix mailqueue, inbound.<br>
The load is negligible until new mail arrives.<br><br>There are not many users on the system at that hour but there could <br>be about 400 mostly idle IMAP connections from webmail (another server)<br>and smartphones, etc. There are 4800 mailboxes, stored on<br>
a partition dedicated to cyrus.<br><br>We use lmtp with postfix. In cyrus.conf:<br><br>lmtpunix cmd="lmtpd" listen="/var/lib/imap/socket/lmtp" prefork=1<br><br>In <a href="http://main.cf">main.cf</a>:<br>
<br>mailbox_transport = lmtp:unix:/var/lib/imap/socket/lmtp<br><br>All of the scanning like clamav, amavis, etc.<br>happens at the MX before it hits this cyrus server.<br><br>The system is a single cyrus box, 8 GB RAM, dual Xeon 3.2 Ghz<br>
(4 cores total) and 4 SAS drives with Perc 5 controller providing RAID 5.<br><br>free command and a cacti graph of memory use shows we have lots<br>of free RAM.<br><br>This system has run since 2009 without issues. It is Redhat Enterprise Linux 5.9<br>
(education version, no support).<br><br>The problem appears quickly, but when I've seen it, the iowait time<br>goes as high as 50%, but briefly.<br><br>I've checked some articles about tuning for cyrus and switched to deadline<br>
scheduler and lower nr_requests value of 4. It may have helped a little but<br>nothing very significant.<br><br>We run these from cyrus.conf:<br><br>EVENTS {<br> squatter cmd="squatter -s -r user" at=0410<br> checkpoint cmd="ctl_cyrusdb -c" period=30<br>
delprune cmd="cyr_expire -E 3" at=0400<br> tlsprune cmd="tls_prune" at=0400<br>}<br><br>We're using the postfix/cyrus packages directly from Redhat.<br>postfix 2.3.3<br>cyrus-imapd 2.3.7<br>
<br>I'm wondering if there is anything more I can check/tweak.<br><br>Is there maintenance we should consider like rebuilding<br>all mailboxes?<br><br><br></div>