Do you sometimes find anvil missing? I wonder if you can strace master and see what it is doing or waiting for...
This happened again this morning. I see the anvil process died -
22815 ? Z 0:13 [anvil] <defunct>
# strace -p 22799 Process 22799 attached - interrupt to quit futex(0xb7bc2bec, FUTEX_WAIT, 2, NULL <unfinished ...>
That's all there was from strace.
I saw your post on the postfix list. Do you really have problems with number of file handles? IIRC file-max is automatically adjusted? On my box it is pretty high at 48520 without any tuning on my part.
What does 'sysctl fs.file-nr' say?