From mboxrd@z Thu Jan 1 00:00:00 1970 From: Lars =?UTF-8?B?VMOkdWJlcg==?= Subject: Re: How to grow RAID1 mirror on top of LVM? Date: Tue, 29 Apr 2008 09:55:45 +0200 Message-ID: <20080429095545.305b2dfd.taeuber@bbaw.de> References: <25F8EF57-9606-4217-B2D4-2DD3D8E064C4@cam.ac.uk> <18408.36712.100712.499844@notabene.brown> <20080428162556.00ee0d72.taeuber@bbaw.de> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: In-Reply-To: Sender: linux-raid-owner@vger.kernel.org To: David Lethe Cc: Neil Brown , Anton Altaparmakov , linux-raid@vger.kernel.org List-Id: linux-raid.ids Hallo David! "David Lethe" schrieb: > Lars: > Even if you *could* do this, then your design would still be an awful= idea. You'd effectively have a random I/O filesystem. Any write on a= RAID1 disk would generate writes on all of the other disks. Even with= a small number of RAID1 targets and default journaling, I wouldn't be = surprised if a single application write translated into at least a doze= n physical disk writes. =20 >=20 > What if (when) both the RAID1 & RAID6 became corrupted? How would yo= u proceed? How would you propose the md engine deal with this? What = if you lose a disk on the RAID6 while expanding the LVM and have a bad = sector on remaining disks, or fsck shows filesytem corruption while you= are expanding a md volume.=20 >=20 > Maybe you are starting to get the point. No, sorry. I really don't understand. But maybe because I didn't tell d= etailed enough what our systems looks like. We have here two huge RAID6 systems, that are connected through a 10G E= thernet switch. They are equally in size. On these RAID6 we create LVs euqally in size and want them to be parts = of a RAID1: RAID6 RAID6 monosan duosan LV LV (multiple of) \ / 10GE RAID1 | 10GE aoe | 1GE server (multiple of) > What is preventing the md layer from doing what you want is that a h= eck of a lot of code would have to be written, But could you tell me what in the current =C2=BBdesign=C2=AB prevents u= s to resize the LVs and the RAID1 on top? When I understand it correctly the RAID information are written at the = end of each accessible partition/LV. What is different on an extended LV from a partition that is replaced w= ith a bigger one? [...] Thanks Lars --=20 Informationstechnologie Berlin-Brandenburgische Akademie der Wissenschaften J=C3=A4gerstrasse 22-23 10117 Berlin Tel.: +49 30 20370-352 http://www.bbaw.de -- To unsubscribe from this list: send the line "unsubscribe linux-raid" i= n the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html