Cannot mount partition on iSCSI LUN

[alzibub]

Distro: Jaunty
Package: open-iscsi-2.0.870.1-0ubuntu3
Iscsi target: openfiler
Expected outcome: mount succeeds
Actual outcome: mount fails
Details:

I am able to log in to my iSCSI LUN using iscsiadm, but when I try to mount the partition I get an error. This used to work on Intrepid, and the same commands currently work when run from a CentOS 5.2 or Debian Lenny host. The commands I am running are:

root@galois:~# iscsiadm -m node -p 10.80.224.21:3260,1 -T iqn.2006-01.com.openfiler:alexz2 -l
Logging in to [iface: default, target: iqn.2006-01.com.openfiler:alexz2, portal: 10.80.224.21,3260]
Login to [iface: default, target: iqn.2006-01.com.openfiler:alexz2, portal: 10.80.224.21,3260]: successful
root@galois:~# mount /dev/disk/by-path/ip-10.80.224.21\:3260-iscsi-iqn.2006-01.com.openfiler\:alexz2-lun-0-part1 /mnt
mount: /dev/sdg1 already mounted or /mnt busy

I think the "already mounted or /mnt busy" message is a red-herring as I am able to mount other filesystems on /mnt with no problems.

The kernel messages all look okay:

Apr 28 10:19:40 galois kernel: [324463.676641] scsi30 : iSCSI Initiator over TCP/IP
Apr 28 10:19:40 galois kernel: [324463.929278] scsi 30:0:0:0: Direct-Access OPNFILER VIRTUAL-DISK 0 PQ: 0 ANSI: 4
Apr 28 10:19:40 galois kernel: [324463.930571] sd 30:0:0:0: [sdg] 20971520 512-byte hardware sectors: (10.7 GB/10.0 GiB)
Apr 28 10:19:40 galois kernel: [324463.934014] sd 30:0:0:0: [sdg] Write Protect is off
Apr 28 10:19:40 galois kernel: [324463.935164] sd 30:0:0:0: [sdg] Write cache: disabled, read cache: enabled, doesn't support DPO or FUA
Apr 28 10:19:40 galois kernel: [324463.935842] sd 30:0:0:0: [sdg] 20971520 512-byte hardware sectors: (10.7 GB/10.0 GiB)
Apr 28 10:19:40 galois kernel: [324463.936397] sd 30:0:0:0: [sdg] Write Protect is off
Apr 28 10:19:40 galois kernel: [324463.936967] sd 30:0:0:0: [sdg] Write cache: disabled, read cache: enabled, doesn't support DPO or FUA
Apr 28 10:19:40 galois kernel: [324463.936970] sdg: sdg1 sdg2
Apr 28 10:19:40 galois kernel: [324463.953384] sd 30:0:0:0: [sdg] Attached SCSI disk
Apr 28 10:19:40 galois kernel: [324463.953441] sd 30:0:0:0: Attached scsi generic sg2 type 0

[alzibub (alex-zeffertt)]

Got it!

There's a conflict between open-iscsi and multipath-tools. After removing multipath-tools, mounting iSCSI LUNs works fine! So there are two options:

 1. quick fix: mark the conflict in the package meta-data so that they cannot be installed simultaneously
 2. slow fix: work out why mounting iSCSI LUNs fails if multipath-tools are installed and fix it.

Personally, I don't mind which..., I'm now happy.

Regards,

Alex Zeffertt

[sseitz (s-seitz)]

Just for the records: This bug is reproducable since Ubuntu Gutsty and renders Ubuntu virtually useless for Virtualization Servers with HA iSCSI connectivity.

[alzibub (alex-zeffertt)]

Hi,

Just out of interest... which virtualization server requires both
open-iscsi and multipath-tools?

Regards,

Alex

2009/5/23 sseitz <email address hidden>:
> Just for the records: This bug is reproducable since Ubuntu Gutsty and
> renders Ubuntu virtually useless for Virtualization Servers with HA
> iSCSI connectivity.
>
> --
> Cannot mount partition on iSCSI LUN
> https://bugs.launchpad.net/bugs/368491
> You received this bug notification because you are a direct subscriber
> of the bug.
>

[alzibub (alex-zeffertt)]

This is not a bug, please close this ticket.

When the multipath-tools package is installed, the device-mapper takes exclusive control of new disks - provided they are not blacklisted in multipath.conf. It does this so that it can create a "multipath" device node. This is so that when a disk is discovered with the same wwid it can be added under the "multipath" device node.

For example, if the iscsi initiator logs in to a target and /dev/sdg is created, this will be taken by device-mapper which will then create a node under /dev/mapper/ corresponding to /dev/sdg. If the iscsi initiator logs into another target and /dev/sdh is created, and this has the same wwid as /dev/sdg, then device-mapper recognises that they are alternate paths to the same LUN and attaches /dev/sdh to the same node under /dev/mapper.

So the solution is just to try and mount the node under /dev/mapper instead of the /dev/sd* node, if multipath-tools are installed.

Sorry for the confusion - I didn't realise when I raised this bug that I had multipath-tools installed. Or even what multipath-tools was for!

Alex