Date: Wed, 23 Sep 2009 12:54:59 -0400 From: Tony Holmes <tony@crosswinds.net> To: freebsd-geom@FreeBSD.org Subject: Mirrors and Stripes and Bad Disks, Oh My Message-ID: <20090923165459.GA95498@crosswinds.net>
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Hi All, I have a system set up with 4 disks ad4/ad6/ad8/ad10 in a combination of RAID 1 and RAID 10. ad4/ad8 and ad6/ad10 are mirrored (gm0 and gm1 respectively). I have set up mirrored disks as per http://onlamp.com/pub/a/bsd/2005/11/10/FreeBSD_Basics.html I have put 4 partitions on both pairs. The first 4 partitions of each are /, /var, /usr, /tmp. The last partition on both mirror sets are striped and used for /usr/home. Ok, ad8 dropped out - no biggie but I didn't notice it for a couple days. On Resync, ad4 has hard read errors. It rebooted in the process, marking ad8 as the master and ad4 as dirty (when the ad4->ad8 resynch failed!!) ad8 does need to be replaced as well as it has flaked out after a long period of time (could just be power/cable, but I don't trust it). So now I'm up a river a little and could use some guidance. I need to preserve the data on the stripe, swap out ad8 and ad4. I know that geom metadata is indepedant of the partition data. I need to get ad4 back as the master in the mirror without losing actual data. So I was thinking of doing the following - and geom/disk experts please jump in if you see any problem: 1. Bring up the system in single user mode. 2. Destroy gm0 (with ad4 and ad8) 3. Recreate gm0 with ad4 only 4. Break ad10 out of the gm1 mirror pair - this way during recovery I can build another copy of the stripe using ad8/ad10 if I need it. I expect to hit bad sectors on the copy off. I also do expect lost files/data if I have to go this route due to the time that ad8 was not mirrored. Will this give me gm0 with a master ad4? If I am able to recreate the stripe with identical parameters, will the file system be visible. It's a pita and yes I can recover most from backups but not a couple critical files that went on today (of course). TIA for any assistance. -- Tony Holmes Ph: (416) 993-1219 Founder and Senior Systems Architect Crosswinds Internet Communications Inc.
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