Re: mdadm create to existing raid5
Guy Watkins wrote: } [EMAIL PROTECTED] On Behalf Of Jon Collette } I wasn't thinking and did a mdadm --create to my existing raid5 instead } of --assemble. The syncing process ran and now its not mountable. Is } there anyway to recover from this? Maybe. Not really sure. But don't do anything until someone that really knows answers! I agree - Yes, maybe. What I think... If you did a create with the exact same parameters the data should not have changed. But you can't mount so you must have used different parameters. I'd agree. Only 1 disk was written to during the create. Yep. Only that disk was changed. Yep. If you remove the 1 disk and do another create with the original parameters and put missing for the 1 disk your array will be back to normal, but degraded. Once you confirm this you can add back the 1 disk. Yep. **WARNING** **WARNING** **WARNING** At this point you are relatively safe (!) but as soon as you do an 'add' and initiate another resync then if you got it wrong you will have toasted your data completely!!! **WARNING** **WARNING** **WARNING** You must be able to determine which disk was written to. I don't know how to do that unless you have the output from mdadm -D during the create/syncing. Do you know the *exact* command you issued when you did the initial --create? Do you know the *exact* command you issued when you did the bogus --create? And what version of mdadm you are using? Neil said that it's mdadm, not the kernel, that determines which device is initially degraded during a create. We can look at the code and your command line and guess which device mdadm chose. (Getting this wrong won't matter but it may make recovery quicker.) assuming you have a 4 device raid using /dev/sda1, /dev/sdb1, /dev/sdc1, /dev/sdd1 you'll then do something like: mdadm --create --verbose /dev/md0 --level=5 --raid-devices=4 /dev/sda1 /dev/sdb1 /dev/sdc1 missing try a mount mdadm --create --verbose /dev/md0 --level=5 --raid-devices=4 /dev/sda1 missing /dev/sdc1 /dev/sdb1 try a mount mdadm --create --verbose /dev/md0 --level=5 --raid-devices=4 /dev/sdb1 /dev/sda1 /dev/sdc1 missing try a mount mdadm --create --verbose /dev/md0 --level=5 --raid-devices=4 /dev/sdc1 /dev/sdb1 /dev/sda1 missing try a mount etc etc, So you'll still need to do a trial and error assemble For a simple 4 device array I there are 24 permutations - doable by hand, if you have 5 devices then it's 120, 6 is 720 - getting tricky ;) I'm bored so I'm going to write a script based on something like this: http://www.unix.org.ua/orelly/perl/cookbook/ch04_20.htm Feel free to beat me to it ... The critical thing is that you *must* use 'missing' when doing these trial --create calls. If we've not explained something very well and you don't understand then please ask before trying it out... David - To unsubscribe from this list: send the line unsubscribe linux-raid in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: mdadm create to existing raid5
David Greaves wrote: For a simple 4 device array I there are 24 permutations - doable by hand, if you have 5 devices then it's 120, 6 is 720 - getting tricky ;) Oh, wait, for 4 devices there are 24 permutations - and you need to do it 4 times, substituting 'missing' for each device - so 96 trials. 4320 trials for a 6 device array. Hmm. I've got a 7 device raid 6 - I think I'll go an make a note of how it's put together... grin Have a look at this section and the linked script. I can't test it until later http://linux-raid.osdl.org/index.php/RAID_Recovery http://linux-raid.osdl.org/index.php/Permute_array.pl David - To unsubscribe from this list: send the line unsubscribe linux-raid in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: mdadm create to existing raid5
The mdadm --create with missing instead of a drive is a good idea. Do you actually say missing or just leave out a drive? However doesn't it do a sync everytime you create? So wouldn't you run the risk of corrupting another drive each time? Or does it not sync because of the saying missing? To bad I am intent on learning things the hard way. /etc/mdadm.conf from before I recreated ARRAY /dev/md2 level=raid5 num-devices=4 spares=1 UUID=4f935928:2b7a1633:71d575d6:dab4d6bc /etc/mdadm.conf after I recreated ARRAY /dev/md1 level=raid5 num-devices=4 UUID=81bdd737:901c0a8f:af38cb94:41c4e3da Well before I heard back from you guys . I noticed this problem and in my fountain of infinite wisdom I did mdadm --zero-superblock to all my raid drives and created them again thinking if I got it to look the same it woud just fix it. Well they do look the same now, I am at work or I would give you the new mdadm.conf. I really need to learn patients :( David Greaves wrote: David Greaves wrote: For a simple 4 device array I there are 24 permutations - doable by hand, if you have 5 devices then it's 120, 6 is 720 - getting tricky ;) Oh, wait, for 4 devices there are 24 permutations - and you need to do it 4 times, substituting 'missing' for each device - so 96 trials. 4320 trials for a 6 device array. Hmm. I've got a 7 device raid 6 - I think I'll go an make a note of how it's put together... grin Have a look at this section and the linked script. I can't test it until later http://linux-raid.osdl.org/index.php/RAID_Recovery http://linux-raid.osdl.org/index.php/Permute_array.pl David - To unsubscribe from this list: send the line unsubscribe linux-raid in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html - To unsubscribe from this list: send the line unsubscribe linux-raid in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html
RE: mdadm create to existing raid5
} -Original Message- } From: [EMAIL PROTECTED] [mailto:linux-raid- } [EMAIL PROTECTED] On Behalf Of Jon Collette } Sent: Thursday, July 12, 2007 5:29 PM } To: linux-raid@vger.kernel.org } Subject: mdadm create to existing raid5 } } I wasn't thinking and did a mdadm --create to my existing raid5 instead } of --assemble. The syncing process ran and now its not mountable. Is } there anyway to recover from this? } } Thanks } - } To unsubscribe from this list: send the line unsubscribe linux-raid in } the body of a message to [EMAIL PROTECTED] } More majordomo info at http://vger.kernel.org/majordomo-info.html Maybe. Not really sure. But don't do anything until someone that really knows answers! What I think... If you did a create with the exact same parameters the data should not have changed. But you can't mount so you must have used different parameters. Only 1 disk was written to during the create. Only that disk was changed. If you remove the 1 disk and do another create with the original parameters and put missing for the 1 disk your array will be back to normal, but degraded. Once you confirm this you can add back the 1 disk. You must be able to determine which disk was written to. I don't know how to do that unless you have the output from mdadm -D during the create/syncing. But please don't proceed until someone else confirms what I say or gives better advice! Guy - To unsubscribe from this list: send the line unsubscribe linux-raid in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html
