X-Original-To: pgsql-performance-postgresql.org@localhost.postgresql.org Received: from localhost (av.hub.org [200.46.204.144]) by svr1.postgresql.org (Postfix) with ESMTP id F289ED825F for ; Tue, 20 Sep 2005 04:50:21 -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 71121-05 for ; Tue, 20 Sep 2005 07:50:14 +0000 (GMT) Received: from mxout5.netvision.net.il (mxout5.netvision.net.il [194.90.9.29]) by svr1.postgresql.org (Postfix) with ESMTP id 883B4D80E4 for ; Tue, 20 Sep 2005 04:50:14 -0300 (ADT) Received: from [192.168.0.50] ([194.90.15.25]) by mxout5.netvision.net.il (Sun Java System Messaging Server 6.1 HotFix 0.11 (built Jan 28 2005)) with ESMTP id <0IN3005IGV3P5P60@mxout5.netvision.net.il> for pgsql-performance@postgresql.org; Tue, 20 Sep 2005 10:50:14 +0300 (IDT) Date: Tue, 20 Sep 2005 10:51:41 +0300 From: Michael Ben-Nes Subject: Re: RAID Stripe size In-reply-to: <432F8F1B.7030901@arbash-meinel.com> To: John A Meinel Cc: pgsql-performance@postgresql.org Message-id: <432FBF8D.5010501@canaan.co.il> Organization: Canaan Surfing Ltd MIME-version: 1.0 Content-type: text/plain; charset=UTF-8; format=flowed Content-transfer-encoding: 7BIT X-Accept-Language: en-us, en References: <1126871503.157442.314670@g49g2000cwa.googlegroups.com> <432F8F1B.7030901@arbash-meinel.com> User-Agent: Mozilla Thunderbird 1.0.6 (Windows/20050716) X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, hits=0.091 required=5 tests=[AWL=0.091] X-Spam-Level: X-Archive-Number: 200509/212 X-Sequence-Number: 14520 Hi John A Meinel wrote: >bm\mbn wrote: > > >>Hi Everyone >> >>The machine is IBM x345 with ServeRAID 6i 128mb cache and 6 SCSI 15k >>disks. >> >>2 disks are in RAID1 and hold the OS, SWAP & pg_xlog >>4 disks are in RAID10 and hold the Cluster itself. >> >>the DB will have two major tables 1 with 10 million rows and one with >>100 million rows. >>All the activities against this tables will be SELECT. >> >> > >What type of SELECTs will you be doing? Mostly sequential reads of a >bunch of data, or indexed lookups of random pieces? > > All of them. some Rtree some btree some without using indexes. > > >>Currently the strip size is 8k. I read in many place this is a poor >>setting. >> >> > >>From what I've heard of RAID, if you are doing large sequential >transfers, larger stripe sizes (128k, 256k) generally perform better. >For postgres, though, when you are writing, having the stripe size be >around the same size as your page size (8k) could be advantageous, as >when postgres reads a page, it only reads a single stripe. So if it were >reading a series of pages, each one would come from a different disk. > >I may be wrong about that, though. > > I must admit im a bit amazed how such important parameter is so ambiguous. an optimal strip size can improve the performance of the db significantly. I bet that the difference in performance between a poor stripe setting to an optimal one is more important then how much RAM or CPU you have. I hope to run some tests soon thugh i have limited time on the production server to do such tests. >John >=:-> > > > >>Am i right ? >> >> > > > -- -------------------------- Canaan Surfing Ltd. Internet Service Providers Ben-Nes Michael - Manager Tel: 972-4-6991122 Cel: 972-52-8555757 Fax: 972-4-6990098 http://www.canaan.net.il --------------------------