On Friday July 8, molle.bestefich@xxxxxxxxx wrote: > > So a clean RAID1 with a disk missing should start without --run, just > like a clean RAID5 with a disk missing? Anything degraded needs at least --run or --scan. > > Nevermind, I'll try to reproduce it instead of asking too many questions. > And I suck a bit at testing MD with loop devices, so if someone could > pitch in and tell me what I'm doing wrong here, I'd appreciate it very > much (-: > > # mknod /dev/md0 b 9 0 > # dd if=/dev/zero of=test1 bs=1M count=100 > # dd if=/dev/zero of=test2 bs=1M count=100 > # dd if=/dev/zero of=test3 bs=1M count=100 > # losetup /dev/loop1 test1 > # losetup /dev/loop2 test2 > # losetup /dev/loop3 test3 > # mdadm --create /dev/md0 -l 1 -n 3 /dev/loop1 /dev/loop2 /dev/loop3 > mdadm: array /dev/md0 started. > > # mdadm --detail --scan > /etc/mdadm.conf > # cat /etc/mdadm.conf > ARRAY /dev/md0 level=raid1 num-devices=3 > UUID=1dcc972f:0b856580:05c66483:e14940d8 > devices=/dev/loop/1,/dev/loop/2,/dev/loop/3 /dev/loop/N is reported instead of /dev/loopN because mdadm only has major/minor device numbers to go on and scans /dev, returning the first name it finds. 1.12.0 returns the shortest name it finds. > > # mdadm --stop /dev/md0 > # mdadm --assemble --scan > mdadm: no devices found for /dev/md0 > > // ^^^^^^^^^^^^^^^^^^^^^^^^ ??? Why? The ARRAY line doesn't tell mdadm where to find the array. It only tells mdadm how to recognised the components when they are found(*). The DEVICES line (which you don't have) tells mdadm where to find components. So: echo 'DEVICES /dev/loop?' > /etc/mdadm.conf mdadm --detail --scan >> /etc/mdadm.conf mdadm --stop /dev/md0 mdadm --assemble --scan should work > > # mdadm --assemble /dev/md0 /dev/loop1 /dev/loop2 /dev/loop3 > mdadm: /dev/md0 has been started with 3 drives. > > // So far so good.. > > # mdadm --stop /dev/md0 > # losetup -d /dev/loop3 > # mdadm --assemble /dev/md0 /dev/loop1 /dev/loop2 /dev/loop3 > mdadm: no RAID superblock on /dev/loop7 > mdadm: /dev/loop7 has no superblock - assembly aborted > > // ^^^^^^^^^^^^^^^^^^^^^^^^ ??? It aborts :-(... > // Doesn't an inactive loop device seem the same as a missing disk > to MD? I assume that is loop3, not loop7 ?? You have asked mdadm to assemble /dev/loop1 /dev/loop2 and /dev/loop3 into an array. But it can tell that they are not all parts of the same array (infact loop3 isn't part of an array at all). The only parts of the array that you currently have are on /dev/loop1 and /dev/loop2. So you want to mdadm --assemble /dev/md0 --run /dev/loop1 /dev/loop2 (you need --run to convince mdadm that you know what you are doing). Not that with /dev/loop3 no funcitoning, mdadm --assemble --scan will still work. NeilBrown (*) The mdadm.conf entry > ARRAY /dev/md0 level=raid1 num-devices=3 > UUID=1dcc972f:0b856580:05c66483:e14940d8 > devices=/dev/loop/1,/dev/loop/2,/dev/loop/3 tells mdadm: You can recognise components of /dev/md0 as they have a raid superblock which records the level as 'raid1', the number of devices as '3', the UUID as 1dcc972f:0b856580:05c66483:e14940d8, and they will only be on one of the devices /dev/loop/1, /dev/loop/2, or /dev/loop/3. Normally you will not want the 'devices=' section and mdadm 1.12.0 won't report if unless you give a '-v'. NeilBrown - 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
