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

Re: Bumping block size to 16K on FreeBSD...

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Sean Chittenden <sean(at)chittenden(dot)org>
Cc: pgsql-hackers(at)postgresql(dot)org
Subject: Re: Bumping block size to 16K on FreeBSD...
Date: 2003-08-28 22:43:48
Message-ID: 29461.1062110628@sss.pgh.pa.us (view raw or flat)
Thread:
Lists: pgsql-hackers
Sean Chittenden <sean(at)chittenden(dot)org> writes:
> Early performance tests on my laptop suggest it's about 8% faster for
> writing when both the FS and PostgreSQL use 16K blocks.

BTW, I don't really believe that one set of tests, conducted on one
single machine, are anywhere near enough justification for changing this
value.  Especially not if it's a laptop rather than a typical server
configuration.  You've got considerably less I/O bandwidth in proportion
to CPU horsepower than a server.  Why is that an issue?  Well, a larger
block size will substantially increase our WAL overhead (because we tend
to dump whole blocks into WAL at the slightest provocation) and on
slower machines the CRC64 calculations involved in WAL entries are a
significant cost.  On a machine with less CPU and more disk horsepower
than you tested, the tradeoffs could be a lot different.

			regards, tom lane

In response to

Responses

pgsql-hackers by date

Next:From: Dennis GearonDate: 2003-08-28 22:52:24
Subject: Re: Replication Ideas
Previous:From: Thomas SwanDate: 2003-08-28 22:36:22
Subject: Re: Bumping block size to 16K on FreeBSD...

Privacy Policy | About PostgreSQL
Copyright © 1996-2014 The PostgreSQL Global Development Group