On 08/19/2016 01:18 PM, Chris Maxwell wrote: <snip> > https://raid.wiki.kernel.org/index.php/RAID_Recovery suggest one can create rather than assemble a sw raid. (Not sure whether to call it md0 or md1) > mdadm --create /dev/md0 --metadata=0.90 --raid-devices=2 --level=raid1 /dev/sdb1 missing > > However, the it also says > >> Recreating should be considered a *last* resort, only to be used when everything else fails. People getting this wrong is one of the primary reasons >> people lose data. It is very commonly used way too early in the fault finding process. You have been warned! It's better to send an email to the >> linux-raid mailing list with detailed information (mdadm --examine from all component drives plus log entries from when the failure happened, >> including mdadm and kernel version) and ask for advice than to try to use --create --assume-clean and getting it wrong. > > > > So before I messed things up even worse, I figured I would consult the experts to see what my next step should be. I am not an expert but 0.9 metadata is at the end, and the md device is a simple mirror. I don't know why the underlying device couldn't be used directly. I think this should work, depending on your hardware raid: * verify exact size of md device by looking at size of /dev/md0 block device assembled from failing /dev/sdc1 * copy partition layout from /dev/sdc using sfdisk -d * pull both sdb1 and sdc1 drives (mark which drive goes where) * put in 2 new drives to replace failing sdc * initialize new drives in hardware raid * observe no existing partition table on new device * create partition table on new device using sfdisk * create a new md device /dev/md1 on the new /dev/sd?1, verifying size of /dev/md1 block device is same or bigger than original /dev/md0 * add good drives from original sdb back * make an overlay of the first partition of the good device https://raid.wiki.kernel.org/index.php/Recovering_a_failed_software_RAID#Making_the_harddisks_read-only_using_an_overlay_file * zero the metadata on the overlay with mdadm --zero-superblock /path/to/overlay * dd data from /path/to/overlay onto /dev/md1. This will run out of room if the new md device is exactly the same size as the old one, but should copy all the actual data. --Sarah -- 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
