Date: Wed, 25 Jan 2012 11:16:25 +0900 (JST) From: Hiroki Sato <hrs@FreeBSD.org> To: wblock@wonkity.com Cc: freebsd-doc@FreeBSD.org Subject: Re: Handbook RAID1 example Message-ID: <20120125.111625.2289296443525755896.hrs@allbsd.org> In-Reply-To: <alpine.BSF.2.00.1201231536490.92721@wonkity.com> References: <alpine.BSF.2.00.1201231536490.92721@wonkity.com>
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----Security_Multipart(Wed_Jan_25_11_16_25_2012_175)-- Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit Warren Block <wblock@wonkity.com> wrote in <alpine.BSF.2.00.1201231536490.92721@wonkity.com>: wb> Multiple users on the forums have reported problems with existing wb> gmirror(8) mirrors being unbootable after upgrading to FreeBSD 9: wb> http://forums.freebsd.org/showthread.php?t=28895 wb> wb> The workaround is to set kern.geom.part.check_integrity="0" in wb> /boot/loader.conf. wb> wb> wb> The example from the RAID1 chapter of the Handbook isn't helping: wb> http://www.freebsd.org/doc/en_US.ISO8859-1/books/handbook/geom-mirror.html wb> wb> The procedure overrides the safety and uses the last block of a drive, wb> regardless of whether it was already allocated to a partition. During wb> boot, the GEOM system sees the error and stops: wb> wb> GEOM_MIRROR: Device mirror/gm0 launched (2/2). wb> GEOM_PART: partition 1 has end offset beyond last LBA: 1250263727 > wb> 1250263726 wb> GEOM_PART: integrity check failed (mirror/gm0, MBR) wb> wb> To be fair, that example allows (allowed) the user to set up a mirror wb> of their existing disk complete with whatever partitioning existed. wb> And it still ought to work if the last block was not part of a wb> partition. wb> wb> That Handbook chapter could be updated without a huge change by wb> removing the instructions to turn off the safety (so it will error out wb> if the user tries it on an allocated last block). wb> wb> Then add a note or warning along the lines of "The procedure shown can wb> only be used if the last block of the drive has not been already wb> allocated to a partition. If the last block has been included in a wb> partition, back up, repartion leaving at least one unused block at the wb> end of the drive, create the mirror, and restore." I think we should rewrite this section not to create a malformed partition table by configuring gmirror in some way. If all of partitions are UFS, the following procedure should be safe: 1. gmirror label gm0 /dev/da1, and edit /boot/loader.conf to load the kernel module. 2. Reboot and check if gm0 is recognized even after that (just in case). 3. Create partitions in /dev/mirror/gm0 based on ones in /dev/da0. If capacity of /dev/da0 and /dev/da1 is the same as each other gm0 should be slightly smaller by the last sector. 4. Dump & restore each partition from /dev/da0* to /dev/mirror/gm0*. Install a boot block if necessary. 5. mount /dev/mirror/gm0s1a /mnt, and edit /mnt/etc/fstab to mount gm0. Also, apply the same change to /etc/fstab in /dev/da0. 6. Reboot and check if gm0 is mounted as the root partition. 7. gmirror add gm0 /dev/da0, and wait for the rebuild. The primary difference between the above and one in the handbook is to use /dev/da1 for gm0 first. By doing this, both making a backup of /dev/da0 and repartitioning before setting up the mirror configuration can be done virtually. The step 3 may be complex in some cases, but I personally think partitioning /dev/mirror/gm0 by gpart based on the existing /dev/da0 is not so difficult. -- Hiroki ----Security_Multipart(Wed_Jan_25_11_16_25_2012_175)-- Content-Type: application/pgp-signature Content-Transfer-Encoding: 7bit -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.11 (FreeBSD) iEYEABECAAYFAk8fZfkACgkQTyzT2CeTzy1+egCfcioSyok0uywyDI458JuL2MnL 6dcAoN2XhGZGoEs8J8ztLQh6U82hcTQX =Q1Vo -----END PGP SIGNATURE----- ----Security_Multipart(Wed_Jan_25_11_16_25_2012_175)----
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