On Sat, 29 Jan 2005, T. Ermlich wrote: > Hello there, > > I just got here from http://cgi.cse.unsw.edu.au/~neilb/Contact ... > Hopefully I'm more/less right here. > > Several month ago I set-up an raid1 using mdadm. > Two drives (/dev/sda & /dev/sdb, each one is an 160GB Samsung SATA > disks) are used, and provide now /dev/md0, /dev/md1, /dev/md2 & > /dev/md3. In november 2004 I upgraded to mdadm 1.8.1. Drop 1.8.1 and get 1.8.0. I understand 1.8.1 has some experimental code and not designed to be used for real. > This afternoon, about 9 hours ago, /dev/sda broke down ... no chnace to > get it working again .. :( > > My question now is: what does I have to do now? Well, go through the procedure to remove the disk and put a new one back in... > The system is up and running, so I'd do an actual backup of the most > important data ... but how to 'replace' the broken drive, and 'restore' > the data content there (sorry, as english is not my native language I > have no idea how to explain it correctly). > Is there a way to do so, or does I have to create an raid1 from scratch, > and copy all data from /dev/md0-3 there manually? You should not have to copy it - thats the whole point of it all, however, RAID is not a substitute for proper backups, so make sure you do those backups now and regularly in the future. OK - here are the basic steps - you may have to modify them as you haven't posted enough detail for me to work it out to your exact system. I'm assuing that you have partitioned each disk with 4 partitions and both disks are partitioned identically and you are combining the same partition of each device into the md devices. (eg. /dev/md0 is made from /dev/sda1 and /dev/sdb1) This is reasonably "sane" and I'm sure lots of people do it this way (I do, but I'm a small sample :) If you aren't doing it this way, then this won't work for you, but you may be able to adapt it for your needs. Firstly, get mdadm 1.8.0 as I mentioned above. Look at /proc/mdstat. See if all 4 md devices have a failed device in it. If the disk is really dead, this is likely to be the case, if it's not, then you'll need to fail each partition in each md device: So make make sure that each md device has the failed disk really failed, you can do: mdadm --fail /dev/md0 /dev/sda1 mdadm --fail /dev/md1 /dev/sda2 mdadm --fail /dev/md2 /dev/sda3 mdadm --fail /dev/md3 /dev/sda4 Next, you need to remove the failed disk from each array mdadm --remove /dev/md0 /dev/sda1 mdadm --remove /dev/md1 /dev/sda2 mdadm --remove /dev/md2 /dev/sda3 mdadm --remove /dev/md3 /dev/sda4 Strictly speaking, you don't have to do this - you can just power down and put a new disk in, but I feel this is "cleaner" and hopefully leaves the system in a stable and known state when you do power down. At this point you can power down the machine and physically remove the drive and replace it with a new, identical unit. Reboot your PC. If it would normally boot off sda, you have to persuade it to boot off sdb. You might need to alter the bios to do this, ot maybe not... All BIOSes and controllers have their own little ideas about how this is done. If it boots off another drive (eg. an IDE drive) then you should be fine. If it does boot off sda, then I hope you used the raid-extra-boot command in lilo.conf (and tested it...) If you are using grub, I can't be of any assistance there as I don't use it. You should now have the system running with the data intact on sdb and all the md devices working and mounted as normal. Now you have to re-partition the new sda identical to sdb. If they are the same make and size, you can use this: sfdisk -d /dev/sdb | sfdisk /dev/sda Now, tell the raid code to re-mirror the drives: mdadm --add /dev/md0 /dev/sda1 mdadm --add /dev/md1 /dev/sda2 mdadm --add /dev/md2 /dev/sda3 mdadm --add /dev/md3 /dev/sda4 then run: watch -n1 cat /proc/mdstat and wait for it to finish, however the system is fully usable all during this process. If you can't power the machine down, and have hot-swappable drives in proper caddys, then there is a way to tell the kernel that you are removing the drive and adding a new one in, however it's probably safer if you can do it while powered down. If this doesn't make sense, post back the output of /proc/mdstat and fdisk -l Goos luck! Gordon - To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
