On 7/8/05, Neil Brown <neilb@xxxxxxxxxxxxxxx> wrote: > On Thursday July 7, molle.bestefich@xxxxxxxxx wrote: > > Mitchell Laks wrote: > > > However I think that raids should boot as long as they are intact, as a matter > > > of policy. Otherwise we lose our ability to rely upon them for remote > > > servers... > > > > It does seem wrong that a RAID 5 starts OK with a disk missing, but a > > RAID 1 fails. > > > > Perhaps MD is unable to tell which disk in the RAID 1 is the freshest > > and therefore refuses to assemble any RAID 1's with disks missing? > > This doesn't sound right at all. > > "--run" is required to start a degraded array as a way of confirming > to mdadm that you really have listed all the drives available. > The normal way of starting an array at boot time is by describing the > array (usually by UUID) in mdadm.conf and letting mdadm find the > component devices with "mdadm --assemble --scan". > > This usage does not require --run. > > The only time there is a real reluctance to start a degraded array is > when it is raid5/6 and it suffered an unclean shutdown. > A dirty, degraded raid5/6 can have undetectably data corruption, and I > really want you to be aware of that and not just assume that "because > it started, the data must be OK". Sounds very sane. So a clean RAID1 with a disk missing should start without --run, just like a clean RAID5 with a disk missing? 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 # mdadm --stop /dev/md0 # mdadm --assemble --scan mdadm: no devices found for /dev/md0 // ^^^^^^^^^^^^^^^^^^^^^^^^ ??? Why? # 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? # rm -f /dev/loop3 # mdadm --assemble /dev/md0 /dev/loop1 /dev/loop2 /dev/loop3 mdadm: cannot open device /dev/loop7: No such file or directory mdadm: /dev/loop7 has no superblock - assembly aborted // ^^^^^^^^^^^^^^^^^^^^^^^^ ??? It aborts, just as above... Hm! - 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
