Thanks, the --zero-superblock on the device I want to re-add worked. I think I understand what happened, possibly as a result of some mdadm improvements. A verbose explanation follows.
The complexity I did not share, is that my three-disk RAID1 array is actually between two laptops, each which can sync-to/from an eSATA. In my case, both my laptop disks were previously operating as active disks in an array at the same time (both technically degraded, one with two members, the other with only one member). The external drive had been in sync with my second laptop, running 11.10. My first laptop which was last synced a few days ago and has now been upgraded to 12.04B1 while operating with one member. As soon as I deemed 12.04 functionally great, I immediately shut them both down, and tried to do my usual pre-login swap of active disks on the first (12.04) laptop to my external drive where my current home directory was residing. Normally this works just un-mounting/failing/removing/stopping the devices and re-assembling/re-mounting with the external member. Now, I believe mdadm is smart enough to know that both disks came from active/clean (albeit degraded possibly) md disks, and so it chooses not to let me just re-add one to another as I see fit. Previously, the most recent would be the active if I boot with both attached, and a re-sync would start immediately OR I could start with one member, and switch to another. Now mdadm blocks if I try and add one previously active member to another when they are out of sync, waiting for me to clear meta on the old active member. This is improved, I will just change my process in this situation based on these assumptions. -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/945786 Title: mdadm refuses to re-add failed member To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/mdadm/+bug/945786/+subscriptions -- ubuntu-bugs mailing list [email protected] https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
