Fedora server consuming all memory and grinding to a halt

[Langdon Stevenson]

Hi,

I have three Fedora server (two are F8, one is F6) that have all been
running (literally) for years.  They are all in different
locations/networks but for an unknown reason all of them have used up
all of their ram and stopped responding to ssh, ping etc.  This happened
at different times to each machine over the last two weeks.

Rebooting resolves the problem and it has not re-occurred as yet.

I can find no indication in the logs that anything odd was happening.

Two of the servers have http and SMTP open to the Internet, but one
doesn't.  Two are connected to each other, one isn't.  There doesn't
seem to be any common vulnerability (like a common process exposed to
the Internet)

Given these servers' perfect record in the past I am wondering if anyone
can suggest what might be going on?  Or how best to try to track down
the reason.

Langdon