DM-Multipath Weirdness with NetApp Storage

Latest response

Our enterprise normally uses EMC for block-mode storage. However, one of our tenants apparently has to use NetApp for block-mode. Because this is a rare configuration, haven't really done NetApp block-mode on RHEL since 2010.

The normal DM-multipath procedures work, for the most path:

  • /dev/mapper/dm-N entries get created for each LUN
  • `multipath -ll`shows device trees for each multipathed LUN
  • I'm able to partition the DM devices
  • I'm able to use kpartx to propagate the partition tables to all of the sdX devices in the dm-N dev-node

Where it gets weird is on reboot. Whem multipathd restarts, three dm-N devices become six. When I trace the devnodes under /dev, I find that the three mystery dm-N devices share major and minor numbers with the dm-NpX devicenodes:

brw-rw----  1 root        disk 253,       7   Jul 18 12:32 /dev/mapper/mpath0
brw-rw----  1 root        root 253,       7   Jul 18 12:32 /dev/dm-7
brw-rw----  1 root        disk 253,       8   Jul 18 12:32 /dev/mapper/mpath1
brw-rw----  1 root        root 253,       8   Jul 18 12:32 /dev/dm-8
brw-rw----  1 root        disk 253,       9   Jul 18 12:32 /dev/mapper/mpath2
brw-rw----  1 root        root 253,       9   Jul 18 12:32 /dev/dm-9
brw-rw----  1 root        disk 253,      10   Jul 18 12:32 /dev/mapper/mpath0p1
brw-rw----  1 root        root 253,      10   Jul 18 12:32 /dev/dm-10
brw-rw----  1 root        disk 253,      11   Jul 18 12:32 /dev/mapper/mpath1p1
brw-rw----  1 root        root 253,      11   Jul 18 12:32 /dev/dm-11
brw-rw----  1 root        disk 253,      12   Jul 18 12:32 /dev/mapper/mpath2p1
brw-rw----  1 root        root 253,      12   Jul 18 12:32 /dev/dm-12

I've verified all my configuration files and everything looks right, DM-multipath just seems to think that it has to create dm-N devices for each partition on the real dm-N devices.

That said, while these nodes show up under /dev and in the output of `fdisk -lu` (though the fdisk output shows them ad devices that are a few GB smaller than the real LUNs and show them as having no partition tables of their own), they don't show up in the `multipath -ll` ouput.

Hopefully, what I've described is clear. I'm writing from home and can't look at the system right now. Anyone run into this before? Tips? Suggestions.

Responses