On Fri, 2012-05-18 at 09:21 -0400, Root Kev wrote: > During the last time that the load went up, it became unable to login / su > to root for the entire period that dovecot was running, we had to kill > dovecot and go back to Popa3d until the mailq was cleared up. We are > running CentOS 5.6 server. Based on TOP running at the time the CPU usage > was running under 10%. Once Dovecot was killed, we were then able to log > in /su again.
Like Kelsey said, a very high disk IO might explain this, although normally the login should still eventually succeed. Another thing I'm wondering is if some process limit reached. How does the login/su fail, does it just hang or immediately fail with some error? > We were under the impression that checking to shadow directly should be the > fastest and least amount of overhead, is any of the other ways to connect > have less load on authentication to PAM? Your passwords really are in /etc/shadow file, not LDAP/something else? I don't think the problem is with authentication. Reading /etc/shadow is pretty fast (unless maybe if it's a huge file) and it anyway can't block login/su from working.
