Re: scheduling autovacuum at lean hours only.

Rajesh Kumar Mallah  writes:

> our usage pattern is such that peak activity (indicated by load average)
> during day time is 10 times during night hours. Autovacuum just puts
> more pressure to the system. If less stressing version is used then

Yet it may allow a more stable performance in the mid/long term.
Not vacuuming enough, even during peak activity, may lead to
bloat in your DB and poor peak performance even without any
vacuuming, only because the DB will have to scan through a lot of
dead tuples. Unless you're doing full vacuums overnight?

> it shall take longer to complete one cycle,  which would mean  less
> performance for longer time . Less performance queues up queries
> and encourages people to re submit their queries which again
> adds to bogging up the system.

I think this user "problem" should be handled at the application
level. You need to add some "still working" pages/icons etc, or
get sure one running query from a single user prevents another
query from the same user to be run concurrently.

> In our case i feel the hardware is bit underscaled as compared to
> load thats why i think running in lean hours is best of both worlds
> no performance sacrifices and intelligent vacuuming.

IMHO you should still measure how much bloat you produce with
such a strategy. I can talk first-hand, because with only nightly
vacuuming and not so much traffic, we had ever growing bloat
which in the end led to minuscule performance (the culprit was
shared with untuned FSM and friends).

-- 
Guillaume Cottenceau