Skip site navigation (1) Skip section navigation (2)

Re: Insert are going slower ...

From: Josh Berkus <josh(at)agliodbs(dot)com>
To: Hervé Piedvache <herve(at)elma(dot)fr>,pgsql-performance(at)postgresql(dot)org
Cc: Shridhar Daithankar <shridhar(at)frodo(dot)hserus(dot)net>, Hervé Piedvache <footcow(at)noos(dot)fr>
Subject: Re: Insert are going slower ...
Date: 2004-07-18 17:23:21
Message-ID: (view raw, whole thread or download thread mbox)
Lists: pgsql-performance

> Hum ... it's only for speed aspect ... I was using postgresql with this
> option since 7.01 ... and for me fsync=on was so slow ...
> Is it really no time consuming for the system to bring it ON now with
> v7.4.3 ??

Well, I wouldn't do it until you've figured out the current performance 

The issue with having fsync=off is that, if someone yanks the power cord on 
your server, there is a significant chance that you will have to restore the 
database from backup becuase it will be corrupted.   But clearly you've been 
living with that risk for some time.

It *is* true that there is significantly less performance difference between 
7.4 with fsync off and on than there was between 7.1 with fsync off and on.  
But there is still a difference.   In 7.0 and 7.1 (I think), when you turned 
fsync off it turned WAL off completely, resulting in a substantial difference 
in disk activity.   Now, it just stops checkpointing WAL but WAL is still 
recording -- meaning that disk activity decreases some but not a lot.   The 
difference is more noticable the more vulnerable to contention your disk 
system is.

The other reason not to think of fsync=off as a permanent performance tweak is 
that we're likely to remove the option sometime in the next 2 versions, since 
an increasing number of features depend on WAL behavior, and the option is 
largely a legacy of the 7.0 days, when WAL was sometimes buggy and needed to 
be turned off to get the database to start.

Josh Berkus
Aglio Database Solutions
San Francisco

In response to

pgsql-performance by date

Next:From: Andy BallingallDate: 2004-07-19 09:12:12
Subject: Re: Working on huge RAM based datasets
Previous:From: Gaetano MendolaDate: 2004-07-18 09:42:36
Subject: Re: High load average with PostgreSQL 7.4.2 on debian/ibm eserver.

Privacy Policy | About PostgreSQL
Copyright © 1996-2017 The PostgreSQL Global Development Group