Multipath problems with 2.6.8.1

["Jaime Peñalba" <jpenalba@corenetworks.es>]

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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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