X-Original-To: pgsql-performance-postgresql.org@localhost.postgresql.org Received: from localhost (unknown [200.46.204.144]) by svr1.postgresql.org (Postfix) with ESMTP id AC0E65286E for ; Thu, 2 Jun 2005 03:06:42 -0300 (ADT) Received: from svr1.postgresql.org ([200.46.204.71]) by localhost (av.hub.org [200.46.204.144]) (amavisd-new, port 10024) with ESMTP id 68949-10 for ; Thu, 2 Jun 2005 06:06:34 +0000 (GMT) Received: from sss.pgh.pa.us (sss.pgh.pa.us [66.207.139.130]) by svr1.postgresql.org (Postfix) with ESMTP id 9AFCA52864 for ; Thu, 2 Jun 2005 03:06:33 -0300 (ADT) Received: from sss2.sss.pgh.pa.us (tgl@localhost [127.0.0.1]) by sss.pgh.pa.us (8.13.1/8.13.1) with ESMTP id j5266VpV010260; Thu, 2 Jun 2005 02:06:31 -0400 (EDT) To: John A Meinel Cc: KeithW@narrowpathinc.com, PostgreSQL Perform Subject: Re: Moving pg_xlog In-reply-to: <429E2854.1050209@arbash-meinel.com> References: <20050601151618.M48325@narrowpathinc.com> <14825.1117642780@sss.pgh.pa.us> <20050601200610.M12354@narrowpathinc.com> <18210.1117657854@sss.pgh.pa.us> <429E2854.1050209@arbash-meinel.com> Comments: In-reply-to John A Meinel message dated "Wed, 01 Jun 2005 16:27:48 -0500" Date: Thu, 02 Jun 2005 02:06:31 -0400 Message-ID: <10259.1117692391@sss.pgh.pa.us> From: Tom Lane X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, hits=0.006 tagged_above=0 required=5 tests=AWL X-Spam-Level: X-Archive-Number: 200506/26 X-Sequence-Number: 12664 John A Meinel writes: > Tom Lane wrote: >> Now that I think about it, you were (if I understood your layout >> correctly) proposing to put the xlog on your system's root disk. >> This is probably a bad idea for performance, ... > I certainly agree with what you wrote. But my understanding is that if > you only have 2 arrays, then moving xlog onto the array not on the > database is better than having it with the database. It isn't optimum, > but it is better. Because that way there isn't as much contention > between the database and xlog. If the machine isn't doing much else than running the database, then yeah, that may be the best available option. If there are other things going on then you have to think about how much competition there is for the root disk. But the impression I had from the OP's df listing is that he has several disks available ... so he ought to be able to find one that doesn't need to do anything except xlog. regards, tom lane