From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mx1.redhat.com (mx1.redhat.com [172.16.48.31]) by int-mx1.corp.redhat.com (8.13.1/8.13.1) with ESMTP id l6O8mNBl023091 for ; Tue, 24 Jul 2007 04:48:23 -0400 Received: from percy.comedia.it (percy.comedia.it [212.97.59.71]) by mx1.redhat.com (8.13.1/8.13.1) with ESMTP id l6O8mL0m025161 for ; Tue, 24 Jul 2007 04:48:22 -0400 Date: Tue, 24 Jul 2007 10:48:20 +0200 From: Luca Berra Subject: Re: [linux-lvm] Flexible storga: LVM setup on top of mdadm sets. Good idea or not? Message-ID: <20070724084820.GA26108@percy.comedia.it> References: <20070723072320.GB30790@percy.comedia.it> Mime-Version: 1.0 Content-Disposition: inline In-Reply-To: Reply-To: LVM general discussion and development List-Id: LVM general discussion and development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , List-Id: Content-Type: text/plain; charset="us-ascii"; format="flowed" Content-Transfer-Encoding: 7bit To: linux-lvm@redhat.com On Mon, Jul 23, 2007 at 12:43:17PM -0400, Stuart D. Gathman wrote: >On Mon, 23 Jul 2007, Luca Berra wrote: > >> On Sun, Jul 22, 2007 at 02:57:33PM -0400, Stuart D. Gathman wrote: >> >The main drawback to md raid1 is that it always resynchronizes >> >the *entire* partition when a disk goes offline temporarily. I also >> False. md uses bitmaps to avoid this. > >I am using md on dozens of systems up through Centos-5. If there are any >bitmaps, they don't work. Or maybe they are a new feature not in kernel >2.6.18. The only change I've noticed since RH7.3 is that sync speed is no >longer limited to 10K. Or maybe I'm not looking at the right thing. man mdadm Bitmaps are a feature of md since mdadm-2.0 (kernel 2.6.13 or 2.6.14) ... >How would I see these bitmaps in action? man mdadm but basically mdadm -G /dev/md?? -b internal >BTW, to upgrade a 7.2 system to Centos5, I plan to install on a disk >with matching partition sizes and replace boot drive. Is there any >chance that md raid1 will sync from the old system overtop the new? >(Because the new wouild have lower sequence numbers?) Or is there some >kind of UUID in the raid superblock to prevent this? (Of course I plan >to change partition types away from RAID Auto just to be safe...) unfortunately redhat insisted for a long time on using the in-kernel md auto-detect, which iirc just ignores md uuid. i think this is still true in redhat5. changing partition type will prevent this creating the new raid with a different minor will prevent this or change the minor of the old raid. ... but we're getting offtopic. if you have further questions post them on linux-raid. L. -- Luca Berra -- bluca@comedia.it Communication Media & Services S.r.l. /"\ \ / ASCII RIBBON CAMPAIGN X AGAINST HTML MAIL / \