I've noticed that on one of my VPSes ( debian 5 lenny ) ( not my linode ones but a host I used prior to linode ), the filesystem is very, very sluggish past midnight.
If I try to use the command line at all, it stalls. At some point after an hour or two, everything goes back to normal and it becomes usable.
Could it potentially be that the server was compromised? Has anyone run into something like this before?