Re: Maximum Performance Follow-up Question

From: "Peter T(dot) Brown" <peter(at)memeticsystems(dot)com>
To: "'Tom Lane'" <tgl(at)sss(dot)pgh(dot)pa(dot)us>, "'Radu-Adrian Popescu'" <radu(dot)popescu(at)aldratech(dot)com>
Cc: "'Postgres Admin List'" <pgsql-admin(at)postgresql(dot)org>
Subject: Re: Maximum Performance Follow-up Question
Date: 2002-01-25 19:44:50
Message-ID: 002101c1a5d8$c09b5990$7d00000a@PETER
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Actually, a great many of the queries we run are Very dependant on
inserts -- we do inserts into a big 'pointers' table and use that as a basis
for other queries. Its also the case that for our web tracking application
nearly every select is paried with an insert (lookup a visitor, add a row
recording their hit to the website). So I think that gaining efficiency on
inserts would really help...

Is there any BIG risk in turning fsync off? I mean, if I miss the last 30
minutes of tracking data from our website because of a system crash, thats
no big deal to me. If the entire database gets corrupted and must be
scrubbed, that's a big deal.

And isn't there some way to use fsync but just use it less frequently, so
that postgres writes a bunch of changes to disk when it less busy or
something?

Thanks

-----Original Message-----
From: Tom Lane [mailto:tgl(at)sss(dot)pgh(dot)pa(dot)us]
Sent: Friday, January 25, 2002 7:24 AM
To: Radu-Adrian Popescu
Cc: Peter T. Brown; Postgres Admin List
Subject: Re: [ADMIN] Maximum Performance Follow-up Question

Radu-Adrian Popescu <radu(dot)popescu(at)aldratech(dot)com> writes:
> I belive you should set
> fsync=false
> in case you mainly select and do inserts rather rare.

No, that's a really horrid reason to turn off fsync. A read-only
transaction never syncs and thus has no fsync penalty. If update
performance isn't a serious problem for you, you may as well keep
fsync on and not have to worry about data loss in the case of a
system crash.

regards, tom lane

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