Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754050AbXFPHvo (ORCPT ); Sat, 16 Jun 2007 03:51:44 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751204AbXFPHvf (ORCPT ); Sat, 16 Jun 2007 03:51:35 -0400 Received: from dsl081-033-126.lax1.dsl.speakeasy.net ([64.81.33.126]:40554 "EHLO bifrost.lang.hm" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750713AbXFPHve (ORCPT ); Sat, 16 Jun 2007 03:51:34 -0400 Date: Sat, 16 Jun 2007 00:48:57 -0700 (PDT) From: david@lang.hm X-X-Sender: dlang@asgard.lang.hm To: Neil Brown cc: Wakko Warner , linux-kernel@vger.kernel.org, linux-raid@vger.kernel.org Subject: Re: limits on raid In-Reply-To: <18035.23867.576212.859440@notabene.brown> Message-ID: References: <18034.479.256870.600360@notabene.brown> <18034.3676.477575.490448@notabene.brown> <20070616020320.GB2002@animx.eu.org> <18035.23867.576212.859440@notabene.brown> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII; format=flowed Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1627 Lines: 34 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. 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. David Lang - 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/