pg_clog & vacuum oddness

I have a machine that typically runs good, but more and more recently
when vacuum runs everything (not just pg) comes to a griding halt.  If
iostat is to be believed, there isn't too much IO going on - 300kB/sec
write, 0kB read.

Now before we diagnose this as "bah!" I noticed something odd - in my
pg_clog directory I have [currently] 384 files. there seem to be about
3-6/day in there. They all (except for hte last) have the same size of
200someodd-kB.

The DB is fairly active with around 20-100 (varies wildly)
insert/update/delete a second.  I had vacuum & fsm tuned so my UnUsed
was rather steady.

The thing that bothers me most is why all that stuff in the clog?
There are entries in there that are older than the last time I spun PG.


Machine is a 2xp3-800mhz, 2gb, linux 2.2.17 [old], pg 7.3.4

--
Jeff Trout <jeff@jefftrout.com>
http://www.jefftrout.com/
http://www.stuarthamm.net/