X-Original-To: pgsql-performance-postgresql.org@localhost.postgresql.org Received: from localhost (av.hub.org [200.46.204.144]) by postgresql.org (Postfix) with ESMTP id EB7F89DC80E for ; Sat, 25 Feb 2006 02:10:59 -0400 (AST) Received: from postgresql.org ([200.46.204.71]) by localhost (av.hub.org [200.46.204.144]) (amavisd-new, port 10024) with ESMTP id 78750-01 for ; Sat, 25 Feb 2006 02:10:59 -0400 (AST) X-Greylist: from auto-whitelisted by SQLgrey- Received: from linda-5.paradise.net.nz (bm-5a.paradise.net.nz [203.96.152.184]) by postgresql.org (Postfix) with ESMTP id AF5F39DCA80 for ; Sat, 25 Feb 2006 02:10:57 -0400 (AST) Received: from smtp-3.paradise.net.nz (tclsnelb1-src-1.paradise.net.nz [203.96.152.172]) by linda-5.paradise.net.nz (Paradise.net.nz) with ESMTP id <0IV8006DPBU9Z6@linda-5.paradise.net.nz> for pgsql-performance@postgresql.org; Sat, 25 Feb 2006 19:10:57 +1300 (NZDT) Received: from [192.168.1.11] (218-101-28-236.dsl.clear.net.nz [218.101.28.236]) by smtp-3.paradise.net.nz (Postfix) with ESMTP id 8E5CCD43E4E; Sat, 25 Feb 2006 19:10:56 +1300 (NZDT) Date: Sat, 25 Feb 2006 19:10:55 +1300 From: Mark Kirkwood Subject: Re: Reliability recommendations In-reply-to: To: Luke Lonergan Cc: Dan Gorman , "Joshua D. Drake" , "Craig A. James" , pgsql-performance@postgresql.org Message-id: <43FFF4EF.6060601@paradise.net.nz> MIME-version: 1.0 Content-type: text/plain; charset=UTF-7 Content-transfer-encoding: 7bit X-Accept-Language: en-us, en User-Agent: Mozilla Thunderbird 1.0.6 (X11/20051106) References: X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, score=0.193 required=5 tests=[AWL=0.193] X-Spam-Score: 0.193 X-Spam-Level: X-Archive-Number: 200602/402 X-Sequence-Number: 17388 Luke Lonergan wrote: > > OK, how about some proof? > > In a synthetic test that writes 32GB of sequential 8k pages on a machine > with 16GB of RAM: > ========================= Write test results ============================== > time bash -c "dd if=/dev/zero of=/dbfast1/llonergan/bigfile bs=8k > count=2000000 && sync" & > time bash -c "dd if=/dev/zero of=/dbfast3/llonergan/bigfile bs=8k > count=2000000 && sync" & > > 2000000 records in > 2000000 records out > 2000000 records in > 2000000 records out > > real 1m0.046s > user 0m0.270s > sys 0m30.008s > > real 1m0.047s > user 0m0.287s > sys 0m30.675s > > So that's 32,000 MB written in 60.05 seconds, which is 533MB/s sustained > with two threads. > Well, since this is always fun (2G memory, 3Ware 7506, 4xPATA), writing: $ dd if=/dev/zero of=/data0/dump/bigfile bs=8k count=500000 500000+0 records in 500000+0 records out 4096000000 bytes transferred in 32.619208 secs (125570185 bytes/sec) > Now to read the same files in parallel: > ========================= Read test results ============================== > sync > time dd of=/dev/null if=/dbfast1/llonergan/bigfile bs=8k & > time dd of=/dev/null if=/dbfast3/llonergan/bigfile bs=8k & > > 2000000 records in > 2000000 records out > > real 0m39.849s > user 0m0.282s > sys 0m22.294s > 2000000 records in > 2000000 records out > > real 0m40.410s > user 0m0.251s > sys 0m22.515s > > And that's 32,000MB in 40.4 seconds, or 792MB/s sustained from disk (not > memory). > Reading: $ dd of=/dev/null if=/data0/dump/bigfile bs=8k count=500000 500000+0 records in 500000+0 records out 4096000000 bytes transferred in 24.067298 secs (170189442 bytes/sec) Ok - didn't quite get my quoted 175MB/s, (FWIW if bs=32k I get exactly 175MB/s). Hmmm - a bit humbled by Luke's machinery :-), however, mine is probably competitive on (MB/s)/$.... It would be interesting to see what Dan's system would do on a purely sequential workload - as 40-50MB of purely random IO is high. Cheers Mark