I have a 512 MB VPS running on Debian Squeeze 64bit serving a complete email system (postfix, courier, amavis, clamav, spamassassin, roundcube). All the RAM is always used: max free memory is 10MB, min is 0 MB. The Swap is 2 GB and is almost not used (5-15 MB max).
I have read that this situation is not so bad, because all the ram is used but there is not much need of relying on disk io, so I should not get any performance issues.
Is this true ? What other parameters should I monitor to detect load levels that affect performance ?
Subquestion: about half the ram is taken by amavis and clamd, is there a way to lower memory usage by these software ?