I have seen the same behavior with Lucid, my machine was up for about one month and during that time I have experienced big I/O waits several times.
I found gnome-power-manager to be the source of the problem so last time I had it I logged some info about the case.
The result was: in 6 minutes gnome-power-manager memory consumption has grown from 372MB (which can hardly be called normal, I guess) to 569MB. (Details: http://pastebin.com/YjFjZcqV )
I have seen the same behavior with Lucid, my machine was up for about one month and during that time I have experienced big I/O waits several times.
I found gnome-power-manager to be the source of the problem so last time I had it I logged some info about the case.
The result was: in 6 minutes gnome-power-manager memory consumption has grown from 372MB (which can hardly be called normal, I guess) to 569MB. (Details: http:// pastebin. com/YjFjZcqV )
Restarting it is a working workaround of course.