Greetings, I run my own email server for some domains I administer, on a centos vps server with a very small number of users.

The only services are smtp, imap/pop, webmail

Everything was running without problems until this morning. I left home for 1/2 hours, and when I came back everything had become about 100x slower (seriously!). The services were/are still all up and running, but practically unusable (even running mutt in my ssh session is almost frozen).

I have not changed/updated anything in the last 1/2 weeks. I have already done a few checks with the VPS provider, and it looks like:

network & hardware are OK

there seem to be no strange processes running. I didn't manage to save the output of "top", but it didn't show anything that (AFAICT, of course) should not be there on an email server

however, there is something that is using "much more memory than normal" (see the comment below from the hosting sysadmin after he checked user_beancounters). Initially we thought it was apache, but even switching it off didn't change anything. What now?

Any help to understand what the heck happened, and find out what exactly _started_ to cause this problem is very welcome!

TIA, Marco

root@vps [/etc/sysconfig]# cat /proc/user_beancounters Version: 2.5 uid resource held maxheld barrier limit failcnt 712: kmemsize 17208298 162267136 2147483646 2147483646 0 lockedpages 0 8 999999 999999 0 privvmpages 64694 262143 262144 262144 40 shmpages 14 2366 131072 131072 0 dummy 0 0 0 0 0 numproc 63 237 999999 999999 0 physpages 79977 262204 0 262144 0 vmguarpages 0 0 131072 2147483647 0 oomguarpages 30261 44087 131072 2147483647 0 numtcpsock 31 243 7999992 7999992 0 numflock 9 20 999999 999999 0 numpty 1 1 500000 500000 0 numsiginfo 0 27 999999 999999 0 tcpsndbuf 545000 7915960 214748160 396774400 0 tcprcvbuf 507904 3981312 214748160 396774400 0 othersockbuf 21832 1229736 214748160 396774400 0 dgramrcvbuf 0 118400 214748160 396774400 0 numothersock 56 356 7999992 7999992 0 dcachesize 10775271 154640329 2147483646 2147483646 0 numfile 772 1155 23999976 23999976 0 dummy 0 0 0 0 0 dummy 0 0 0 0 0 dummy 0 0 0 0 0 numiptent 57 57 999999 999999 0

As you can see, there are some fails for the privvmpages. This means your VPS tried to use more RAM than what is available (e.g. more than 1GB RAM). If you are only running some basic mail services on your VPS, that's definitely not normal and you should investigate that accordingly. We have fully checked everything for hardware and network problems and everything is working flawlessly. In combination with the RAM shortage errors, it is safe to conclude that there's something within your VPS itself that's malfunctioning.