On 07/26/2016 03:47 PM, Chris Murphy wrote: >> So basically I just need to fix the partition table on sdc, > No just remove the GPT signatures, "45 46 49 20 50 41 52 54" and the > PMBR signature "55 aa" from the two drives. > > Restoring the primary GPT on sdd overwrote part of the mdadm metadata. > I'm not sure if --readd alone will fix that, or if one of the > --update= options is necessary as well, and if so which one. OK, Here is where I need a bit more help. Would I use 'dd' to write the zeros at some offset?, or was your mention of wipefs earlier intended as the approach to take (e.g., "wipefs -b -t or -o to remove the GPT signatures, while avoiding the mdadm and file system signatures.") The real question for me is what is the effect of having /dev/sdc1 and /dev/sdd1 as unused partitions on the drive while I'm using the whole drive. Is that something that can bite me later? Right now I understand I have a couple of options: Option 1: attempt a re-add of /dev/sdd to the md4 array currently running in degraded mode. Do I need to delete sdd1 now while the disk is not being used before attempting a re-add sdd to the md4 array? Does it matter? Then if that can be successfully readded/synced, do I care about the fact that sdc has sdc1 on it and should I then --fail --remove sdc, fix the GPT header, delete sdc1 and then readd sdc to the md4 array? (or just leave as and ignore the GPT header issue reported by gdisk?) Option 2: shrink the filesystem on sdc so it will fit in sdc1 and move the filesystem to the sdc1 partition before re-adding. (this I don't understand as well -- how to move the shrunken filesystem from sdc to sdc1?) If I understand, moving to sdc1 doesn't buy me anything and isn't necessary here. So we can strike option 2 if this is correct. Option 3: If it all fails, and I start from scratch, what is the best way to wipe both drives completely to make sure there is no lingering trace of a superblock, etc. before recreating array? # mdadm -S /dev/md4 # mdadm --zero-superblock /dev/sdc # mdadm --zero-superblock /dev/sdd # gdisk to 'fix' /dev/sdc # mdadm --create --verbose /dev/md4 --level=1 --metadata=1.2 \ --raid-devices=2 /dev/sdc1 /dev/sdd1 # mkfs.ext4 -v -L data -m 0.005 -b 4096 -E stride=16,stripe-width=32 /dev/md4 # update mdadm.conf # (recopy data) So it looks like it boils down to: (a) do I need to worry about removing unused sdc1/sdd1? Then do I need to use 'dd' or 'wipefs' to fix the GPT and PMBR signatures on sdc (and I assume do nothing to sdd if I don't need to delete sdd1) (b) nuke it all and start over (if so what is the plan above OK?) I'll try the re-add of sdd to a and report back after your response. -- David C. Rankin, J.D.,P.E. -- 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
