From oracle-l-bounce@freelists.org Thu Sep 9 15:47:13 2004 Return-Path: Received: from air189.startdedicated.com (root@localhost) by orafaq.com (8.11.6/8.11.6) with ESMTP id i89KlDg32322 for ; Thu, 9 Sep 2004 15:47:13 -0500 X-ClientAddr: 206.53.239.180 Received: from turing.freelists.org (freelists-180.iquest.net [206.53.239.180]) by air189.startdedicated.com (8.11.6/8.11.6) with ESMTP id i89KlDI32317 for ; Thu, 9 Sep 2004 15:47:13 -0500 Received: from localhost (localhost [127.0.0.1]) by turing.freelists.org (Avenir Technologies Mail Multiplex) with ESMTP id 6852C72DAE9; Thu, 9 Sep 2004 15:48:48 -0500 (EST) Received: from turing.freelists.org ([127.0.0.1]) by localhost (turing [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id 22106-89; Thu, 9 Sep 2004 15:48:48 -0500 (EST) Received: from turing (localhost [127.0.0.1]) by turing.freelists.org (Avenir Technologies Mail Multiplex) with ESMTP id CAEBA72D71D; Thu, 9 Sep 2004 15:48:47 -0500 (EST) In-Reply-To: <1757383522.20040909225806@rs.lv> To: edgar.chupit@rs.lv Cc: Oracle-L@freelists.org, oracle-l-bounce@freelists.org Subject: Re: Re[2]: Raid5 Vs Raid0+1 -- Raw Vs Solaris 9 Concurrent Direct IO UFS MIME-Version: 1.0 Message-ID: From: J.Velikanovs@alise.lv Date: Thu, 9 Sep 2004 23:50:47 +0300 X-MIMETrack: Serialize by Router on ROSS/IT ALISE/LV(Release 5.0.11 |July 24, 2002) at 2004.09.09 23:50:47, Serialize complete at 2004.09.09 23:50:47 Content-type: text/plain Content-Transfer-Encoding: 8bit X-archive-position: 9339 X-ecartis-version: Ecartis v1.0.0 Sender: oracle-l-bounce@freelists.org Errors-To: oracle-l-bounce@freelists.org X-original-sender: J.Velikanovs@alise.lv Precedence: normal Reply-To: J.Velikanovs@alise.lv X-list: oracle-l X-Virus-Scanned: by amavisd-new at freelists.org Thank you Edgar for your interest, I have read “Is RAID5 Really a Bargain?” http://www.hotsos.com/e-library/abstract.php?id=11 as well as “db_file_mutliblock_read_count and physical IO” ORACLE-L thread, before ask my question. I thought about RAID5 as you described. However Cary in his paper “Is RAID5 Really a Bargain?” and in ORACLE-L thread have mentioned “R + 4W” formula regardless of spins count in RAID. Why “R + 4W”, I wonder? I assume that the way how it can be is: 1. regardless of spin count RAID5 use 3+1 formula 2. to make single “small” write, we need to touch all chunks of RAID5 (3+1) Please correct me. Jurijs PS I am going to read http://www.miracleas.dk/BAARF/0.Millsap1996.08.21-VLDB.pdf On 09.09.2004 22:58:06 oracle-l-bounce wrote: >Dear Jurijs, > >>>- Level 1: would have to process (R + W) I/O requests per second >>>- Level 5: would have to process (R + 4W) I/O requests per second > >JVal> Can I kindly ask you to clarify few questions? >JVal> 1. Is 4W figure (in formula above) constant in context of RAID 5 array and >JVal> not depend on spindles count? I suspect that it can be constant in any >JVal> RAID5 implementation. In case of 6 spindles block will be distributed as: > >Unless I'm missing something than according to raid specs it doesn't >mater how many disks are in raid5 array, you just need one additional >disk for checksums, so in case of 6 spindle array you can create raid5 >that will operate according to your schema (it actually will be two >raid5 arrays) or you can create one raid5 array that will use 5 disks >for data and one disk for checksums. > >Please, correct me if I'm wrong. > >JVal> 2. If we need to change one of 3 data blocks belonging to one RAID5 set, >JVal> block. Do I understand correctly? So for writing one block into RAID5 we >JVal> need 2W+2R. Or I am wrong? > >Actually it's 6 step process something similar to 2W+2C+2R where 2C is >for cpu service. For more information read excelent article by Cary >Millsap (http://www.miracleas.dk/BAARF/0.Millsap1996.08.21-VLDB.pdf) >at page 11. > >-- >Best regards, >Edgar > >-- >To unsubscribe - mailto:oracle-l-request@freelists.org&subject=unsubscribe >To search the archives - http://www.freelists.org/archives/oracle-l/ -- To unsubscribe - mailto:oracle-l-request@freelists.org&subject=unsubscribe To search the archives - http://www.freelists.org/archives/oracle-l/