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<sdb1> md: bind<sdd1> 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: <none>
----------------------------------
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<sdd1> 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 Peñalba 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: <none>
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: <none>
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.
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