Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757913AbXFQRQg (ORCPT ); Sun, 17 Jun 2007 13:16:36 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754823AbXFQRQ0 (ORCPT ); Sun, 17 Jun 2007 13:16:26 -0400 Received: from mail.tmr.com ([64.65.253.246]:35445 "EHLO gaimboi.tmr.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751818AbXFQRQZ (ORCPT ); Sun, 17 Jun 2007 13:16:25 -0400 Message-ID: <46756C6E.1070106@tmr.com> Date: Sun, 17 Jun 2007 13:16:30 -0400 From: Bill Davidsen Organization: TMR Associates Inc, Schenectady NY User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.8.0.8) Gecko/20061105 SeaMonkey/1.0.6 MIME-Version: 1.0 To: david@lang.hm CC: Neil Brown , Wakko Warner , linux-kernel@vger.kernel.org, linux-raid@vger.kernel.org Subject: Re: limits on raid References: <18034.479.256870.600360@notabene.brown> <18034.3676.477575.490448@notabene.brown> <20070616020320.GB2002@animx.eu.org> <18035.23867.576212.859440@notabene.brown> In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1994 Lines: 43 david@lang.hm wrote: > On Sat, 16 Jun 2007, Neil Brown wrote: > >> It would be possible to have a 'this is not initialised' flag on the >> array, and if that is not set, always do a reconstruct-write rather >> than a read-modify-write. But the first time you have an unclean >> shutdown you are going to resync all the parity anyway (unless you >> have a bitmap....) so you may as well resync at the start. >> >> And why is it such a big deal anyway? The initial resync doesn't stop >> you from using the array. I guess if you wanted to put an array into >> production instantly and couldn't afford any slowdown due to resync, >> then you might want to skip the initial resync.... but is that really >> likely? > > in my case it takes 2+ days to resync the array before I can do any > performance testing with it. for some reason it's only doing the > rebuild at ~5M/sec (even though I've increased the min and max rebuild > speeds and a dd to the array seems to be ~44M/sec, even during the > rebuild) > > I want to test several configurations, from a 45 disk raid6 to a 45 > disk raid0. at 2-3 days per test (or longer, depending on the tests) > this becomes a very slow process. > I've been doing stuff like this, but I just build the array on a partition per drive so the init is livable. For the stuff I'm doing a total of 500-100GB is ample to do performance testing. > also, when a rebuild is slow enough (and has enough of a performance > impact) it's not uncommon to want to operate in degraded mode just > long enought oget to a maintinance window and then recreate the array > and reload from backup. -- bill davidsen CTO TMR Associates, Inc Doing interesting things with small computers since 1979 - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/