Performance Woes

Hi,

I have several databases.  They are each about 35gb in size and have about 10.5K relations (count from pg_stat_all_tables) in them.  Pg_class is about 26k rows and the data directory contains about 70k files.  These are busy machines, they run about 50 xactions per second, ( aproxx insert / update / delete about 500 rows per second).

We started getting errors about the number of open file descriptors

: 2007-05-09 03:07:50.083 GMT 1146975740: LOG:  53000: out of file descriptors: Too many open files; release and retry

2007-05-09 03:07:50.083 GMT 1146975740: CONTEXT:  SQL statement "insert ….. "

        PL/pgSQL function "trigfunc_whatever" line 50 at execute statement

2007-05-09 03:07:50.083 GMT 1146975740: LOCATION:  BasicOpenFile, fd.c:471

2007-05-09 03:07:50.091 GMT 0: LOG:  00000: duration: 12.362 ms

2007-05-09 03:07:50.091 GMT 0: LOCATION:  exec_simple_query, postgres.c:1090

So  we decreased the max_files_per_process to 800.  This took care of the error *BUT* about quadrupled  the IO wait that is happening on the machine. It went from a peek of about 50% to peeks of over 200% (4 processor machines, 4 gigs ram, raid).  The load on the machine remained constant.

I am really to get an understanding of exactly what this setting is and ‘what’ is out of file descriptors and how I can fix that.  I need to bring that IO back down.

Thanks for any help.

Ralph