Received: from localhost (maia-2.hub.org [200.46.204.187]) by postgresql.org (Postfix) with ESMTP id 50E7C9FB3A2 for ; Wed, 6 Jun 2007 18:37:12 -0300 (ADT) Received: from postgresql.org ([200.46.204.71]) by localhost (mx1.hub.org [200.46.204.187]) (amavisd-maia, port 10024) with ESMTP id 58530-09 for ; Wed, 6 Jun 2007 18:37:05 -0300 (ADT) X-Greylist: from auto-whitelisted by SQLgrey-1.7.5 Received: from serv01.siteground137.com (ns1.siteground137.com [67.15.250.10]) by postgresql.org (Postfix) with ESMTP id 95C649FB380 for ; Wed, 6 Jun 2007 18:37:08 -0300 (ADT) Received: from nat.vinton.com ([209.162.219.253]:52743 helo=dogma.v10.wvs) by serv01.siteground137.com with esmtpa (Exim 4.52) id 1Hw3Bb-00065e-Ry; Wed, 06 Jun 2007 16:37:00 -0500 Subject: Re: Is this true? From: Jeff Davis To: Chris Hoover Cc: PGSQL Performance In-Reply-To: <1d219a6f0706061358i49823219iee0354b357b4dd02@mail.gmail.com> References: <1d219a6f0706061358i49823219iee0354b357b4dd02@mail.gmail.com> Content-Type: text/plain Date: Wed, 06 Jun 2007 14:37:04 -0700 Message-Id: <1181165824.7660.157.camel@dogma.v10.wvs> Mime-Version: 1.0 X-Mailer: Evolution 2.0.4 (2.0.4-7) Content-Transfer-Encoding: 7bit X-AntiAbuse: This header was added to track abuse, please include it with any abuse report X-AntiAbuse: Primary Hostname - serv01.siteground137.com X-AntiAbuse: Original Domain - postgresql.org X-AntiAbuse: Originator/Caller UID/GID - [0 0] / [47 12] X-AntiAbuse: Sender Address Domain - j-davis.com X-Source: X-Source-Args: X-Source-Dir: X-Virus-Scanned: Maia Mailguard 1.0.1 X-Archive-Number: 200706/112 X-Sequence-Number: 25145 On Wed, 2007-06-06 at 16:58 -0400, Chris Hoover wrote: > Question, > > Does (pg_stat_get_db_blocks_fetched(oid)-pg_stat_get_db_blocks_hit > (oid)*8) = number of KB read from disk for the listed database since > the last server startup? That will give you the number of blocks requested from the OS. The OS does it's own caching, and so many of those reads might come from the OS buffer cache, and not the disk itself. Also, if you're concerned with the number since the last server restart, make sure you have stats_reset_on_server_start set appropriately. Regards, Jeff Davis