From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mx3.redhat.com (mx3.redhat.com [172.16.48.32]) by int-mx1.corp.redhat.com (8.12.11.20060308/8.12.11) with ESMTP id k441dloe012363 for ; Wed, 3 May 2006 21:39:47 -0400 Received: from linux.interlinx.bc.ca (linux.interlinx.bc.ca [66.11.173.224]) by mx3.redhat.com (8.13.1/8.13.1) with ESMTP id k441de0s021029 for ; Wed, 3 May 2006 21:39:41 -0400 Received: from pc.local (pc.ilinx [10.75.22.1]) (using TLSv1 with cipher RC4-MD5 (128/128 bits)) (No client certificate requested) by linux.interlinx.bc.ca (Postfix) with ESMTP id F2E6ADBBD6 for ; Wed, 3 May 2006 21:39:38 -0400 (EDT) From: "Brian J. Murrell" Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="=-gASFiyM2RtZ/BOwFfH3O" Date: Wed, 03 May 2006 21:39:36 -0400 Message-Id: <1146706776.31003.136.camel@pc.local> Mime-Version: 1.0 Subject: [linux-lvm] VG defragmenting and backing up the extent map 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: To: linux-lvm@redhat.com --=-gASFiyM2RtZ/BOwFfH3O Content-Type: text/plain Content-Transfer-Encoding: quoted-printable It has often occurred to me that the fact that a logical volume is not contiguous will make recovery in the face of a partial disaster more difficult. For example, if I happen to lose the logical->physical extent map in the LVM superblock (the single only place this information is kept AFAIK) then I am pretty screwed with respect to getting my filesystems back off the disk. Compared with just losing the partition table from a traditionally partitioned disk, I could use a tool like findsuper and losetup the whole disk with offsets (losetup -o to retrieve the individual filesystems. This technique would even work with LVM given that I had lost the part of the disk with the extent mapping except that my filesystems are not contiguous if I have extended any of them. So, the question is, has anyone developed a tool to "defragment" a Volume Group so that all of the logical volumes in it are contiguous? On a somewhat related note, what provisions can I take to mitigate the loss of the extent map? I am correct in that only one copy of it exists at the head of a Physical Volume? Can I make a backup of it in any way so that it could be used at a later date to reconstruct logical volumes? As you might have guessed, I have lost a small portion of a 160GB disk, the portion which has the extent mapping for the whole PV and I want to mitigate this problem in the future. b. --=20 My other computer is your Microsoft Windows server. Brian J. Murrell --=-gASFiyM2RtZ/BOwFfH3O Content-Type: application/pgp-signature; name=signature.asc Content-Description: This is a digitally signed message part -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.2.2 (GNU/Linux) iD8DBQBEWVtYl3EQlGLyuXARAi8JAJ9fXpj4Wiek7cXZnyeAt4OZOEBX3gCgsr2s d4LrGINbJwIY0cVWIo3Ll24= =TRoA -----END PGP SIGNATURE----- --=-gASFiyM2RtZ/BOwFfH3O--