Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933135Ab0BPRY2 (ORCPT ); Tue, 16 Feb 2010 12:24:28 -0500 Received: from mail.tmr.com ([64.65.253.246]:38947 "EHLO partygirl.tmr.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752576Ab0BPRY0 (ORCPT ); Tue, 16 Feb 2010 12:24:26 -0500 Message-ID: <4B7AD4C4.4090209@tmr.com> Date: Tue, 16 Feb 2010 12:24:20 -0500 From: Bill Davidsen Organization: TMR Associates Inc, Schenectady NY User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.8.1.21) Gecko/20090507 Fedora/1.1.16-1.fc9 NOT Firefox/3.0.11 pango-text SeaMonkey/1.1.16 MIME-Version: 1.0 To: Neil Brown CC: Justin Piszcz , linux-raid@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: Linux mdadm superblock question. References: <20100216115036.0f6b7bb6@notabene.brown> In-Reply-To: <20100216115036.0f6b7bb6@notabene.brown> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2406 Lines: 58 Neil Brown wrote: > On Thu, 11 Feb 2010 18:00:23 -0500 (EST) > Justin Piszcz wrote: > > >> Hi, >> >> I may be converting a host to ext4 and was curious, is 0.90 still the only >> superblock version for mdadm/raid-1 that you can boot from without having >> to create an initrd/etc? >> >> Are there any benefits to using a superblock > 0.90 for a raid-1 boot >> volume < 2TB? >> > > The only noticeable differences that I can think of are: > 1/ If you reboot during recovery of a spare, then 0.90 will restart the > recovery at the start, while 1.x will restart from where it was up to. > 2/ The /sys/class/block/mdXX/md/dev-YYY/errors counter is reset on each > re-assembly with 0.90, but is preserved across stop/start with 1.x > 3/ If your partition starts on a multiple of 64K from the start of the > device and is the last partition and contains 0.90 metadata, then > mdadm can get confused by it. > Given that 4k sector drives make that a lot more likely that it used to be, I suspect some effort will be needed to address this sooner or later. > 4/ If you move the devices to a host with a different arch and different > byte-ordering, then extra effort will be needed to see the array for > 0.90, but not for 1.x > > I suspect none of these is a big issue. > > It is likely that future extensions will only be supported on 1.x metadata. > For example I hope to add support for storing a bad-block list, so that a > read error during recovery will only be fatal for that block, not the whole > recovery process. This is unlikely ever to be supported on 0.90. However > it may not be possible to hot-enable it on 1.x either, depending on how much > space has been reserved for extra metadata, so there is no guarantee that > using 1.x now makes you future-proof. > > And yes, 0.90 is still the only superblock version that supports in-kernel > autodetect, and I have no intention of adding in-kernel autodetect for any > other version. > -- Bill Davidsen "We can't solve today's problems by using the same thinking we used in creating them." - Einstein -- 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/