Redmine

Hi,

Our company uses open source software most of the time.
One of it is RedMine, and it has been running smoothly for the past two years.
This morning, however, there was a sudden spike in memory usage in the server (which has never happened before),
and we do not know the reason for this.
I/O usage was also was very high.
How do we start to investigate this, and what do we do to resolve this problem?
Is there something to be done on the server itself? Or is the redmine application itself causing problems?

Thx,
ana