I'v a Linux server running under Debian Lenny with 4Go of RAM. It doesn't run a large number of stuffs:
Postfix/spamassassin (daemon mode) Bind9 KVM (one guest - 1Go of RAM for it) Every day at exactly 3:05 UTC, the server completely drop to ground floor almost all of its memory. After that, I'v more than 2 G used by buffer and never cleaned up (unless I manually tell the kernel to drop the cache).
I'v searched the web a lot and, at the begining, I though this was due to NFS buffer usage. I do backup over an NFS share drive using gzip/tar and the backup occured at 3:05.
However, I'm now in a very strange situation because I moved the backup task at 1:40 (it completes in 2 mins) and I still drop all the RAM at 3:05.
In my logs, nothing particular, except that at 03:05:01, cron open a session as root and immediately close it at 03:05:02 without doing anything. Of course, cron has been restarted and I checked the timing of the tasks - again, nothing particular.
Any idea why this happens? Or, any idea about how to track what's using all those buffers?
Thanks for your help,