Here is some different behavior, superblock is writed for both paths, and the superblock for the second path persists on both. 1) create md apache2:~# mdadm --create /dev/md0 -v --force --level multipath --raid-devices=1 /dev/sdb1 --spare-devices=1 /dev/sdd1 mdadm: array /dev/md0 started. md: bind md: bind multipath: array md0 active with 1 out of 1 IO paths MULTIPATH conf printout: --- wd:1 rd:1 disk0, o:1, dev:sdb1 MULTIPATH conf printout: --- wd:1 rd:1 disk0, o:1, dev:sdb1 apache2:~# mdadm --detail /dev/md0 /dev/md0: Version : 00.90.01 Creation Time : Thu Sep 9 17:57:32 2004 Raid Level : multipath Array Size : 10485632 (10.00 GiB 10.74 GB) Raid Devices : 1 Total Devices : 2 Preferred Minor : 0 Persistence : Superblock is persistent Update Time : Thu Sep 9 17:57:32 2004 State : clean Active Devices : 1 Working Devices : 2 Failed Devices : 0 Spare Devices : 1 Number Major Minor RaidDevice State 0 8 17 0 active sync /dev/sdb1 1 8 49 -1 spare /dev/sdd1 UUID : 2a8d2bd1:54255df5:5b4b62b5:136a6e34 Events : 0.42 ---------------------------------- apache2:~# cat /proc/mdstat Personalities : [multipath] md0 : active multipath sdd1[1] sdb1[0] 10485632 blocks [1/1] [U] unused devices: ---------------------------------- apache2:~# mdadm -E /dev/sdb1 /dev/sdb1: Magic : a92b4efc Version : 00.90.00 UUID : 2a8d2bd1:54255df5:5b4b62b5:136a6e34 Creation Time : Thu Sep 9 17:57:32 2004 Raid Level : multipath Device Size : 10485632 (10.00 GiB 10.74 GB) Raid Devices : 1 Total Devices : 2 Preferred Minor : 0 Update Time : Thu Sep 9 17:57:32 2004 State : dirty Active Devices : 1 Working Devices : 2 Failed Devices : 0 Spare Devices : 1 Checksum : 19b4a54c - correct Events : 0.42 Number Major Minor RaidDevice State this 1 8 49 1 spare /dev/sdd1 0 0 8 17 0 active sync /dev/sdb1 1 1 8 49 1 spare /dev/sdd1 ---------------------------------- apache2:~# mdadm -E /dev/sdd1 /dev/sdd1: Magic : a92b4efc Version : 00.90.00 UUID : 2a8d2bd1:54255df5:5b4b62b5:136a6e34 Creation Time : Thu Sep 9 17:57:32 2004 Raid Level : multipath Device Size : 10485632 (10.00 GiB 10.74 GB) Raid Devices : 1 Total Devices : 2 Preferred Minor : 0 Update Time : Thu Sep 9 17:57:32 2004 State : dirty Active Devices : 1 Working Devices : 2 Failed Devices : 0 Spare Devices : 1 Checksum : 19b4a54c - correct Events : 0.42 Number Major Minor RaidDevice State this 1 8 49 1 spare /dev/sdd1 0 0 8 17 0 active sync /dev/sdb1 1 1 8 49 1 spare /dev/sdd1 2) stop md mdadm -S /dev/md0 3) start md again apache2:~# mdadm --assemble /dev/md0 --uuid=2a8d2bd1:54255df5:5b4b62b5:136a6e34 /dev/sdb1 /dev/sdd1 mdadm: failed to add /dev/sdb1 to /dev/md0: Device or resource busy mdadm: /dev/md0 has been started with 1 drive. --------------- md: bind md: export_rdev(sdb1) multipath: array md0 active with 1 out of 1 IO paths --------------- apache2:~# mdadm --detail /dev/md0 /dev/md0: Version : 00.90.01 Creation Time : Thu Sep 9 17:57:32 2004 Raid Level : multipath Array Size : 10485632 (10.00 GiB 10.74 GB) Raid Devices : 1 Total Devices : 1 Preferred Minor : 0 Persistence : Superblock is persistent Update Time : Thu Sep 9 18:00:28 2004 State : clean Active Devices : 1 Working Devices : 1 Failed Devices : 0 Spare Devices : 0 Number Major Minor RaidDevice State 0 8 49 0 active sync /dev/sdd1 UUID : 2a8d2bd1:54255df5:5b4b62b5:136a6e34 Events : 0.43 Jaime. Jaime Peņalba wrote: > Hi, > > Im having some troubles with multipath on a 2.6.8.1 linux kernel. > > Im using 2 QLogic 2344 connected to the SAN, i think that my problem > is related to superblocks, because when i create a new multipath > device, it writes the superblock for both disks and really is the same > disk trought two paths. I have else tried to disable persistent > superblock, but mdadm doesnt support multipath with the build mode. > > Im doing it like this > > 1) Start the md > apache1:~/soft/mdadm-1.7.0# mdadm --create /dev/md0 --force --level > multipath --raid-devices=1 /dev/sdb1 --spare-devices=1 /dev/sdd1 > mdadm: array /dev/md0 started. > > apache1:~/soft/mdadm-1.7.0# cat /proc/mdstat > Personalities : [multipath] > md0 : active multipath sdd1[1] sdb1[0] > 4882304 blocks [1/1] [U] > unused devices: > > This is ok and runs fine, But superblock is only at /dev/sdd1, so no > remount would be possible, or i think so... > > apache1:~/soft/mdadm-1.7.0# mdadm -E /dev/sdb1 > mdadm: No super block found on /dev/sdb1 (Expected magic a92b4efc, got > 00000000) > > apache1:~/soft/mdadm-1.7.0# mdadm -E /dev/sdd1 > /dev/sdd1: > Magic : a92b4efc > Version : 00.90.00 > UUID : af3395fd:fac2b820:2ca7083c:612864e0 > Creation Time : Thu Sep 9 17:20:43 2004 > Raid Level : multipath > Device Size : 4882304 (4.66 GiB 5.00 GB) > Raid Devices : 1 > Total Devices : 2 > Preferred Minor : 0 > > Update Time : Thu Sep 9 17:20:43 2004 > State : dirty > Active Devices : 1 > Working Devices : 2 > Failed Devices : 0 > Spare Devices : 1 > Checksum : 63bc7489 - correct > Events : 0.36 > > > Number Major Minor RaidDevice State > this 1 8 49 1 spare /dev/sdd1 > 0 0 8 17 0 active sync /dev/sdb1 > 1 1 8 49 1 spare /dev/sdd1 > > > > 2) Stop the md > apache1:~/soft/mdadm-1.7.0# mdadm -S /dev/md0 > > > 3) Start the md again > apache1:~/soft/mdadm-1.7.0# mdadm --assemble /dev/md0 > --uuid=af3395fd:fac2b820:2ca7083c:612864e0 /dev/sdb1 /dev/sdd1 > mdadm: no RAID superblock on /dev/sdb1 > mdadm: /dev/sdb1 has wrong uuid. > mdadm: /dev/md0 has been started with 1 drive. > > > apache1:~/soft/mdadm-1.7.0# cat /proc/mdstat > Personalities : [multipath] > md0 : active multipath sdd1[0] > 4882304 blocks [1/1] [U] > unused devices: > > Now things arent working very well.... > > apache1:~/soft/mdadm-1.7.0# mdadm --detail /dev/md0 > /dev/md0: > Version : 00.90.01 > Creation Time : Thu Sep 9 17:20:43 2004 > Raid Level : multipath > Array Size : 4882304 (4.66 GiB 5.00 GB) > Raid Devices : 1 > Total Devices : 1 > Preferred Minor : 0 > Persistence : Superblock is persistent > > Update Time : Thu Sep 9 17:26:21 2004 > State : clean > Active Devices : 1 > Working Devices : 1 > Failed Devices : 0 > Spare Devices : 0 > > > Number Major Minor RaidDevice State > 0 8 49 0 active sync /dev/sdd1 > UUID : af3395fd:fac2b820:2ca7083c:612864e0 > Events : 0.37 > > > I would appreciate very much any help with this. > > Thanks, > Jaime.