Space is almost full on host that stores the performance statistics

What does VOM server fault condition:

Space is almost full on host that stores the performance statistics

mean.  I am seeing this on the server fault tab in VOM for a server that is NOT the VOM server and if I drill down to the host that shows the issue there are no filesystems that have alerts on them and the VOM server has DB on a filesystem which is only 15% used.

Mike