Chris Hoover <[EMAIL PROTECTED]> writes:
> there is 1 exception. Everytime there is work to do, it seems to spike our 
> load from < 1 to a load of 3+ for a short time. This tends to cause 
> significant slowdowns for our customer if they happen to do anything that is 
> causing the database to access the drives. It does not seem to matter how 
> much work there is to do. Cleaning up 1 page/tuple or 15000 page/tuples 
> tends to cause this spike.

No surprise, because vacuum has to read every page of the table to see
if there is anything there to clean up.

> We are running 7.3.4 on Dell 2650 connected to a Dell powervault running 
> raid5.

If you were running something a little newer (8.0) you could use the
vacuum_cost_delay knobs to reduce vacuum's impact on I/O load.

                        regards, tom lane

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