On Mon, 4 May 2009, Dean Manners wrote: > Hey guys, > We have an existing (2yrs running) setup that hasn't > recently changed. But are now, fairly suddenly, having problems with our > IMAP servers experiencing very slow/unusable performance when connecting via > the virtual IP. > > > The setup: > Two "directors" - one active, one standby. > - Debian Sarge, 2.6.20.1 kernels. > - Running Ultramonkey > - Uptimes of: > director01:~# uptime > 22:17:17 up 510 days > director02:~# uptime > 22:17:20 up 238 days
nice uptime. We have to reboot here at least once a month for security patching. If it's happening suddenly, then something is different, although I expect you must have gone through all the likely suspects. I assume it's not hardware as POP works and it's not a config problem with the directors, since they both have it. Since the local IMAP machine (webmail server) isn't having problems, but remote clients are, did someone put in a firewall rule somewhere? Joe > Two "mailget" servers - both active, direct routing with loopback addresses, > running IMAP2 & POP3 services on the same virtual IP. > - Running Dovecot > > All behind a Cisco 6500 switch, running aggregated firewall rules (eg the > same one rule affects both real IP and virtual IP address). > > > The symptoms/troubleshooting so far: > ~ When IMAPing via the virtual IP IMAP responsiveness is very slow and > frequently actions times out. > ~ When IMAPing directly to the real servers there is no apparent performance > issue, with speedy responses from both servers. > ~ POP3 performance is normal, to same real servers via the same virtual IP > as our troubled IMAP connections. > * Tried restarting dovecot on both mailget servers (tyre kick measure) > * Tried failing over the heartbeat/ultramonkey monitor on director01, so > that director02 took over the vip's/LVS. There was still noticeable/sluggish > performance when using the IMAP virtual IP from this 2nd machine though. So > that ruled out my director01 being a problem (was thinking the long uptime > may have been at play). > ~ Our webmail server however connects IMAP the same way via the load > balanced address and appears to have no problems, large'ish mailboxes load > almost instantly and all actions are responsive. The only difference I can > note, is that this server is in the same subnet as the directors/real > servers. > ~ IMAP connections represent about 15% of total mail connections, most use > POP3: > > # ipvsadm --list |grep mail > IP Virtual Server version 1.2.1 (size=4096) > Prot LocalAddress:Port Scheduler Flags > -> RemoteAddress:Port Forward Weight ActiveConn InActConn > TCP mail.myserver.blah:pop3 wlc persistent 600 > -> mailget01.myserver.blah:pop3 Route 1 54 144 > -> mailget02.myserver.blah:pop3 Route 1 59 173 > TCP mail.myserver.blah:imap2 wlc persistent 600 > -> mailget01.myserver.blah:imap Route 1 12 1 > -> mailget02.myserver.blah:imap Route 1 14 16 > > > The ldirectord.cf (note, has been the same for 2+ years): > > # Global Directives > checktimeout=3 > checkinterval=15 > autoreload=yes > quiescent=no > logfile="/var/log/ldirectord.log" > > # Main POP > virtual=xxx.xxx.xx.80:110 > real=xxx.xxx.xx.81:110 gate > real=xxx.xxx.xx.82:110 gate > service=pop > scheduler=wlc > login="[email protected]" > passwd="blahblah" > persistent=600 > protocol=tcp > > # Main IMAP > virtual=xxx.xxx.xx.80:143 > real=xxx.xxx.xx.81:143 gate > real=xxx.xxx.xx.82:143 gate > service=imap > scheduler=wlc > login="[email protected]" > passwd="blahblah" > persistent=600 > protocol=tcp > > > Im at a loss of what to try next, with POP3 and other services (HTTP/HTTPS) > operating as normal from the same directors, no recent changes in configs, > and two directors giving the same symptoms - I cant see where the problem > lies. Any tips on where to start looking ? > > > Regards > __________________________________________ > Dean Manners > > > > _______________________________________________ > Please read the documentation before posting - it's available at: > http://www.linuxvirtualserver.org/ > > LinuxVirtualServer.org mailing list - [email protected] > Send requests to [email protected] > or go to http://lists.graemef.net/mailman/listinfo/lvs-users > -- Joseph Mack NA3T EME(B,D), FM05lw North Carolina jmack (at) wm7d (dot) net - azimuthal equidistant map generator at http://www.wm7d.net/azproj.shtml Homepage http://www.austintek.com/ It's GNU/Linux! _______________________________________________ Please read the documentation before posting - it's available at: http://www.linuxvirtualserver.org/ LinuxVirtualServer.org mailing list - [email protected] Send requests to [email protected] or go to http://lists.graemef.net/mailman/listinfo/lvs-users
