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I have a personal Ubuntu server with nine drives:

  • SSD for OS
  • four 4TB drives for one BTRFS raid10 array
  • four 8TB drives for another BTRFS raid10 array

I decided to clean up the cabling today and moved some drives to different SATA ports. This appears to have been my undoing.

System now starts in Emergency Mode and only three of nine drives receive UUID and are listed under /dev/disk/by-uuid. All nine drives are listed in /dev/sd* and in /dev/disk/by-path. All nine drives can be examined with fdisk -l.

I tried running probepart and blkid on all drives. All of them appear to have a valid UUID on them as per blkid output, but the OS does not recognize it.

Is there anything I can do? I assumed since I was using UUIDs for everything I was allowed to move drives to different SATA ports.

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Ok, after digging I realized this is correct operation. Only one of BTRFS array members will be listed as having UUID in /dev/disk/by-uuid

Examining output of btrfs filesystem show will clearly indicate there are no member devices missing. In fact my two raid10 arrays are accessible.

Therefore I have yet to find out what is causing Emergency Mode.

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