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[linux-lvm] multipath works; lvm on multipath does not



How can I tell what is causing LVM on multipath volumes to fail, while direct multipath volumes are working?


The details:

I have several volumes that are multipathed over fibre channel (2 qlogic cards in the host) from a Fujitsu Eternus 4000 (4 controllers).  

When using a file system mounted on the dm-multipath device directly (Ie.: generating I/O via IOZone), it fails over gracefully when I pull out either of the fibre pairs, and the file system continues to operate.  This device is called /dev/mapper/zimbra-mb1-t2-v4_fujitsu1-lun66.

However, when I access an LVM volume created with sister devices as PVs, the LVM presented volume does not fail over.  Rather the LV device goes inaccessible and the file system (ext3) re-mounts itself as read-only.  If I try to access any of the underlying PVs, they still respond as available (Ie.: fdisk -l $PV).

I am not seeing duplicate devices, and am using the following filter in /etc/lvm/lvm.conf:

 filter = [ "a|^/dev/md.*|", "a|^/dev/mapper/zimbra-mb.*-t.*-v.*_.*-lun.*|", "r|.*|" ]


I have also added the following, but dm-multipath devices seem usable by LVM with or without this setting:

  types = [ "device-mapper", 1 ]


I have tried removing the /etc/lvm/cache/.cache file, but that seems to have had no effect.  I've also tried re-building the initrd after modifying the lvm.conf file, also with no effect.

Additional info:
root zimbra-mb1:~# pvs
  PV                                          VG         Fmt  Attr PSize   PFree  
  /dev/mapper/zimbra-mb1-t1-v1_fujitsu1-lun55 mb1_t1     lvm2 a-   195.31G  60.31G
  /dev/mapper/zimbra-mb1-t1-v2_fujitsu1-lun56 mb1_t1     lvm2 a-   195.31G  60.31G
  /dev/mapper/zimbra-mb1-t1-v3_fujitsu1-lun57 mb1_t1     lvm2 a-   195.31G  60.31G
  /dev/mapper/zimbra-mb1-t1-v4_fujitsu1-lun58 mb1_t1     lvm2 a-   195.31G  60.31G
  /dev/mapper/zimbra-mb1-t2-v1_fujitsu1-lun63 mb1_t2     lvm2 a-   504.00G   4.00G
  /dev/mapper/zimbra-mb1-t2-v2_fujitsu1-lun64 mb1_t2     lvm2 a-   488.28G      0 
  /dev/mapper/zimbra-mb1-t2-v3_fujitsu1-lun65 mb1_t2     lvm2 a-   195.31G 195.31G
  /dev/mapper/zimbra-mb1-t2-v5_fujitsu1-lun67 mb1_t2     lvm2 a-   354.37G      0 
  /dev/mapper/zimbra-mb1-t2-v6_fujitsu1-lun68 mb1_t2     lvm2 a-   234.56G  77.21G
  /dev/md1                                    zimbra-mb1 lvm2 a-   136.50G  83.50G



kernel version:  2.6.24-24-server
distoro:         Ubuntu Hardy
multipath-tools: 0.4.8-7ubuntu2
lvm2:            2.02.26-1ubuntu9

Thanks!

-Brian


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