Hello, I haven't written to this list in a while, the situation I put myself in requires me to ask for some help from this mailing list.
The short story here is I have a 4 disk raid 5 array, where one of my drives died. My array became degraded, I shutdown my home server until I received a new replacement drive. Upon receiving my replacement drive, I used it to replaced the broken drive and booted into single user mode to resync my RAID5 array. At about the 12% mark, another returned a read error and mdadm marked that drive to failed, essentially leaving me with a spare, a failed drive and only 2 drive out 4 in the array. I know, my chances are bleek to recover from this, but I still believe there's hope. Forget about backups, only half of my important files are backed up. I was in the middle of building a bigger NAS to backup my home server. Long story and what I've done. /dev/md0 is assembled with 4 drives /dev/sda3 /dev/sdb3 /dev/sdc3 /dev/sdd3 2 weeks ago, mdadm marked /dev/sda3 as failed. cat /proc/mdstat showed _UUU. smarctl also confirmed that the drive was dying. So I shutdown the server and until I received a replacement drive. This week, I replaced the dying drive with my new drive. Booted into single user mode and did this: mdadm --manage /dev/md0 --add /dev/sda3 a cat of /proc/mdstat confirmed the resyncing process. The last time I checked it was up to 11%. After a few minutes later, I noticed that the syncing stopped. An read error message on /dev/sdd3 (have a pic of it if interested) appear on the console. It appears that /dev/sdd3 might be going bad. A cat /proc/mdstat showed _U_U. Now I panic, and decide to leave everything as is and to go to bed. The next day, I shutdown the server and reboot with a live usb distro (Ubuntu rescue remix). After booting into the live distro, a cat /proc/mdstat showed that my /dev/md0 was detected but all drives had an (S) next to it. i.e. /dev/sda3 (S)... Naturally I don't like the looks of this. I ran ddrescue to copy /dev/sdd onto my new replacement disk (/dev/sda). Everything, worked, ddrescue got only one read error, but was eventually able to read the bad sector on a retry. Tonight I plan to repeat this procedure with ddrescue and to clone /dev/sdb and /dev/sdc. Now is where I need your help. How should I got about to try and rebuild my array? I will be using the cloned drives to do this. My goal is to simply assemble my raid array in degraded state with sdb3, sdc3 and sdd3, mount /dev/md0 and backup as many files as I can. From the various google searches, I was going to first try a: mdadm --assemble --scan #which I expect to not work. mdadm --assemble --force #still not quite sure about the syntax and if ordering is important. I've also seen people using the --assume-clean option. But what commands should I do. Since if I mess-up, starting over, by recloning my drives is a time consuming step.
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