Received: from localhost (unknown [200.46.204.183]) by postgresql.org (Postfix) with ESMTP id BE36B65027E for ; Wed, 13 Aug 2008 16:55:38 -0300 (ADT) Received: from postgresql.org ([200.46.204.86]) by localhost (mx1.hub.org [200.46.204.183]) (amavisd-maia, port 10024) with ESMTP id 27105-05 for ; Wed, 13 Aug 2008 16:54:45 -0300 (ADT) X-Greylist: from auto-whitelisted by SQLgrey-1.7.6 Received: from mac.se (slimjim.mantaray.se [195.43.255.244]) by postgresql.org (Postfix) with ESMTP id ECD3165025B for ; Wed, 13 Aug 2008 16:54:47 -0300 (ADT) Received: from [85.24.169.56] (account henke HELO [10.168.1.146]) by mac.se (CommuniGate Pro SMTP 4.2.10) with ESMTP-TLS id 5393534; Wed, 13 Aug 2008 21:54:43 +0200 Cc: Jeff , david@lang.hm, Luke Lonergan , pgsql-performance@postgresql.org Message-Id: <32CD744F-2C1A-4BE2-B4BA-90CFD3A86DF7@mac.se> From: Henrik To: Decibel! In-Reply-To: <8795DFE4-BFE1-49A5-8341-A6823DF2BE4E@decibel.org> Content-Type: text/plain; charset=US-ASCII; format=flowed; delsp=yes Content-Transfer-Encoding: 7bit Mime-Version: 1.0 (Apple Message framework v928.1) Subject: Re: Filesystem benchmarking for pg 8.3.3 server Date: Wed, 13 Aug 2008 21:54:43 +0200 References: <014F2941B0A1EA47BD61D21526B806E903509704@MI8NYCMAIL08.Mi8.com> <2DBD3E73-D9E5-4DFA-832F-3FD53480B284@torgo.978.org> <8795DFE4-BFE1-49A5-8341-A6823DF2BE4E@decibel.org> X-Mailer: Apple Mail (2.928.1) X-Virus-Scanned: Maia Mailguard 1.0.1 X-Spam-Status: No, hits=0 tagged_above=0 required=5 tests=none X-Spam-Level: X-Archive-Number: 200808/157 X-Sequence-Number: 31038 13 aug 2008 kl. 17.13 skrev Decibel!: > On Aug 11, 2008, at 9:01 AM, Jeff wrote: >> On Aug 11, 2008, at 5:17 AM, Henrik wrote: >> >>> OK, changed the SAS RAID 10 to RAID 5 and now my random writes are >>> handing 112 MB/ sek. So it is almsot twice as fast as the RAID10 >>> with the same disks. Any ideas why? >>> >>> Is the iozone tests faulty? >> >> >> does IOzone disable the os caches? >> If not you need to use a size of 2xRAM for true results. >> >> regardless - the test only took 10 seconds of wall time - which >> isn't very long at all. You'd probably want to run it longer anyway. > > > Additionally, you need to be careful of what size writes you're > using. If you're doing random writes that perfectly align with the > raid stripe size, you'll see virtually no RAID5 overhead, and you'll > get the performance of N-1 drives, as opposed to RAID10 giving you N/ > 2. But it still needs to do 2 reads and 2 writes for every write, correct? I did some bonnie++ tests just to give some new more reasonable numbers. This is with RAID10 on 4 SAS 15k drives with write-back cache. Version 1.03b ------Sequential Output------ --Sequential Input- --Random- -Per Chr- --Block-- -Rewrite- -Per Chr- --Block-- --Seeks-- Machine Size K/sec %CP K/sec %CP K/sec %CP K/sec %CP K/sec %CP /sec %CP safecube04 32136M 73245 95 213092 16 89456 11 64923 81 219341 16 839.9 1 ------Sequential Create------ --------Random Create-------- -Create-- --Read--- -Delete-- -Create-- --Read--- -Delete-- files /sec %CP /sec %CP /sec %CP /sec %CP /sec %CP /sec %CP 16 6178 99 +++++ +++ +++++ +++ 6452 100 +++++ +++ 20633 99 safecube04,32136M, 73245,95,213092,16,89456,11,64923,81,219341,16,839.9,1,16,6178,99,++++ +,+++,+++++,+++,6452,100,+++++,+++,20633,99 > > -- > Decibel!, aka Jim C. Nasby, Database Architect decibel@decibel.org > Give your computer some brain candy! www.distributed.net Team #1828 > >