How to change the exported LUN number on a VIOS "Virtual Target Disk" or VTD

05 November 2010

How to change the exported LUN number on a VIOS "Virtual Target Disk" or VTD

When you create a "Virtual Target Disk" or VTD on a VIOS, there is not documented way to define or change the LUN number that it shows to the client partition. But there are situation where you might need to update it:

In a dual VIOS environment, to have the same LUNs in both clients (easier to administrate)-
In a redudant configuration, when you need to start lpars on different hardware, using SAN disks. For instance, we use this configuration for our Backup datacenter where we have al the SAN disks mirrored.

In this post I comment how to update this LUN. The idea is basicly:

Set the VTD device to Defined in the VIOS
Update the ODM database. You have to update the attribute 'LogicalUnitAddr' in ObjectClass 'CuAt'
Perform a 'cfgmgr' on the virtual host adapter (vhostX). This will enable the VTD device and reload the LUN number. Perform an cfgmgr on the VTD device does not work.

So, with commands:

$ oem_setup_env
# bash

# lsmap -vadapter vhost21
SVSA            Physloc                                      Client Partition ID
--------------- -------------------------------------------- ------------------
vhost21         U9117.MMA.XXXXXXX-V2-C34                     0x00000016

VTD                   host01v01
Status                Available
LUN                   0x8200000000000000
Backing device        hdiskpower0
Physloc               U789D.001.BBBBBBB-P1-C3-T2-L75

# ioscli mkvdev -vadapter vhost21 -dev host01v99 -vdev hdiskpower1
cfgmgr -l vhost21

# lsmap -vadapter vhost21
SVSA            Physloc                                      Client Partition ID
--------------- -------------------------------------------- ------------------
vhost21         U9117.MMA.XXXXXXX-V2-C34                     0x00000016

VTD                   host01v01
Status                Available
LUN                   0x8200000000000000
Backing device        hdiskpower0
Physloc               U789D.001.JJJJJJJ-P1-C3-T2-L75

VTD                   host01v99
Status                Available
LUN                   0x8300000000000000
Backing device        hdiskpower1
Physloc               U789D.001.JJJJJJJ-P1-C3-T2-L77

# rmdev -l host01v99
host01v99 Defined

# odmget -q "name=host01v99 and attribute=LogicalUnitAddr"  CuAt
CuAt:
  name = "host01v99"
  attribute = "LogicalUnitAddr"
  value = "0x8300000000000000"
  type = "R"
  generic = "D"
  rep = "n"
  nls_index = 6

# odmchange -o CuAt -q "name = host01v99 and attribute = LogicalUnitAddr" <<"EOF"
CuAt:
  name = "host01v99"
  attribute = "LogicalUnitAddr"
  value = "0x8100000000000000"
  type = "R"
  generic = "D"
  rep = "n"
  nls_index = 6
EOF

# odmget -q "name=host01v99 and attribute=LogicalUnitAddr"  CuAt
CuAt:
  name = "host01v99"
  attribute = "LogicalUnitAddr"
  value = "0x8100000000000000"
  type = "R"
  generic = "D"
  rep = "n"
  nls_index = 6

# cfgmgr -l vhost21
# lsmap -vadapter vhost21
SVSA            Physloc                                      Client Partition ID
--------------- -------------------------------------------- ------------------
vhost21         U9117.MMA.XXXXXXX-V2-C34                     0x00000016

VTD                   host01v01
Status                Available
LUN                   0x8200000000000000
Backing device        hdiskpower0
Physloc               U789D.001.JJJJJJJ-P1-C3-T2-L75

VTD                   host01v99
Status                Available
LUN                   0x8100000000000000
Backing device        hdiskpower1
Physloc               U789D.001.JJJJJJJ-P1-C3-T2-L77

In the client partition, you can scan for the new disk, and it will have the LUN 0x81:

root@host01:~/# cfgmgr -l vio0
root@host01:~/# lscfg -vl hdisk5
  hdisk5           U9117.MMA.XXXXXXX-V22-C3-T1-L8100000000000000  Virtual SCSI Disk Drive

Note: Actually I changed the output of these commands to remove information of my company.

Update: I created an script to do this: changevtdlun.sh