Hello,

We have the problem with multipathing iscsi devices.

There are two hosts HOST1, HOST2 presented with the same lun LUN1 from EVA. Iscsi-targets (iscsitarget-0.4.12-6) configured on HOST1 and HOST2 presenting LUN1 to another host HOST3.

So, HOST3 takes two iscsi devices (using iscsi-initiator-utils-4.0.3.0-6) HOST1: LUN1.dm-1, HOST2: LUN1.dm-1 targeting the same lun LUN1.

Now, we want to implement redundancy on these devices using multipath (device-mapper-multipath-0.4.5-27.RHEL4).

The problem is that multipath shows two difference paths for above iscsi devices. Please advice, if it is possible, how to configure multipathing as it failovers between two devices and shows one paths.

As I know open-iscsi determines when two different iscsi devices represents the same lun . Problem is that we can’t use open-iscsi as it is not supported on our kernel (2.6.9-67.ELsmp).

Any suggestion is highly appreciable

Whats the output from "multipath -d -ll"?


For reference, my system (fiber channel, not iscsi) will show both paths to the shared LUN, and create a virtual disk to access it by:

# multipath -d -ll
raid03_01 (2001b4d28010083b6) dm-5 JetStor,RAID03 # 01
[size=3.5T][features=0][hwhandler=0]
\_ round-robin 0 [prio=2][active]
\_ 3:0:3:1 sdc 8:144 [active][ready]
\_ 4:0:2:1 sdd 8:224 [active][ready]

# ll /dev/mapper/raid03_01
brw-rw---- 1 root disk 253, 5 Oct 29 13:49 raid03_01



Regards,
Scott

Scott,

thank you.

That's on HOST3:

mpath6 (14945540000000000000000000b000000a92d00000d000000)
[size=50 GB][features="0"][hwhandler="0"]
\_ round-robin 0 [active]
\_ 17:0:0:1 sdb 8:16 [active][ready]

mpath5 (14945540000000000000000000d000000a62d00000d000000)
[size=50 GB][features="0"][hwhandler="0"]
\_ round-robin 0 [active]
\_ 16:0:0:1 sda 8:0 [active][ready]

brw-rw---- 1 root disk 253, 0 Dec 4 05:51 mpath5
brw-rw---- 1 root disk 253, 1 Dec 4 05:51 mpath6


FC works fine. For instance on HOST1 and HOST2 we get.

mpath1 (36001438002a55d5a0000c00000970000)
[size=50 GB][features="1 queue_if_no_path"][hwhandler="0"]
\_ round-robin 0 [active]
\_ 0:0:2:2 sdf 8:80 [active]
\_ 0:0:3:2 sdh 8:112 [active]
\_ 1:0:2:2 sdn 8:208 [active]
\_ 1:0:3:2 sdp 8:240 [active]
\_ round-robin 0 [enabled]
\_ 0:0:0:2 sdb 8:16 [active]
\_ 0:0:1:2 sdd 8:48 [active]
\_ 1:0:0:2 sdj 8:144 [active]
\_ 1:0:1:2 sdl 8:176 [active]

Any suggestion?

multipath -v 3 |more says

all paths in cache :

14945540000000000000000000d000000a62d00000d000000 22:0:0:1 sda 8:0 [active]
14945540000000000000000000e000000a92d00000d000000 23:0:0:1 sdb 8:16 [active]

Thoug they are targeting the same LUN two uid's provided differently by iscsi-initiator. How to reconfigure iscsi-initiator as it gives to multipath the similar uids.

Any word?

Interesting.

I'm not sure how to configure the iscsi-initiator to generate like id's, but perhaps you can use the simpler 0x80 VPD id as a work around.

If the output from the following commands are identical (and don't match other LUN's) you could create a device mapping for them:

/sbin/scsi_id -p 0x80 -g -u -s /block/sda
/sbin/scsi_id -p 0x80 -g -u -s /block/sda


Otherwise, you could probably use the major/minor numbers with dmsetup, though thats more of a hack then a fix.


Sorry, but this is beyond my level of experience.
Scott

Scott,

It works. Now I can see
[root@gcrmobi01 block]# multipath -lll

mpath15 (SIET_____VIRTUAL-DISK_______)
[size=50 GB][features="0"][hwhandler="0"]
\_ round-robin 0 [prio=1][active]
\_ 49:0:0:1 sda 8:0 [active][ready]
\_ round-robin 0 [prio=1][enabled]
\_ 50:0:0:1 sdb 8:16 [active][ready]


However if we add another LUN it can't be handled.

Thank you.

Hi scott,

Just would like to share how it was done.

The problem was in iscsi target. I found the nice info at http://manpages.ubuntu.com/manpages/...ietd.conf.html.
lun entry in ietd.con file update like Lun 1 Path=/dev/mpath/siebelfs,Type=fileio,ScsiId=siebelfs123
ScsiId optional parameter allows iscsi initiator uniquely determine device.

Now, we can see desired output;
issiebelfs (1494554000000000073696562656c66733132330000000000)
[size=50 GB][features="0"][hwhandler="0"]
\_ round-robin 0 [prio=1][active]
\_ 4:0:0:1 sda 8:0 [active][ready]
\_ round-robin 0 [prio=1][enabled]
\_ 5:0:0:1 sdb 8:16 [active][ready]


Thank you.

Good to know - thanks for posting the solution.