Accessing the same LUNs from Client Partitions on different Central Electronics Complex (CEC) modules

Last published : Sep 11, 2026
This section briefly outlines how to set shared storage so that it is visible from client partitions on different CEC modules.
With the VIO server and client partitions set up and ready, make sure that you have installed the right level of operating system on the client partitions, and that you have mapped the physical adapters to the client partitions to provide access to the external shared storage.
To create a shareable diskgroup, you need to ensure that the different partitions use the same set of disks. A good way to make sure that the disks (that are seen from multiple partitions) are the same is to use the disks serial numbers, which are unique.
Run the following commands on the VIO server (in non-root mode), unless otherwise noted.
Get the serial number of the disk of interest:
$ lsdev -dev hdisk20 -vpd
    hdisk20
    U787A.001.DNZ06TT-P1-C6-T1-W500507630308037C-
    L401    0401A00000000  IBM FC 2107

    Manufacturer................IBM
    Machine Type and Model......2107900
    Serial Number...............7548111101A
    EC Level.....................131
    Device Specific.(Z0)........10
    Device Specific.(Z1)........0100
    …
Make sure the other VIO server returns the same serial number. This ensures that you are viewing the same actual physical disk.
List the virtual SCSI adapters.
$ lsdev -virtual | grep vhost
    vhost0  Available  Virtual SCSI Server Adapter
    vhost1  Available  Virtual SCSI Server Adapter
Note: Usually vhost0 is the adapter for the internal disks. vhost1 in the example above maps the SCSI adapter to the external shared storage.
Prior to mapping hdisk20 (in the example) to a SCSI adapter, change the reservation policy on the disk.
$ chdev -dev hdisk20 -attr reserve_policy=no_reserve
hdisk20 changed
For hdisk20 (in the example) to be available to client partitions, map it to a suitable virtual SCSI adapter.
If you now print the reserve policy on hdisk20 the output resembles:
$ lsdev -dev hdisk20 attr reserve_policy
    value
    no_reserve
Next create a virtual device to map hdisk20 to vhost1.
$ mkvdev -vdev hdisk20 -vadapter vhost1 -dev mp1_hdisk5
    mp1_hdisk5 Available
Finally on the client partition run the cfgmgr command to make this disk visible via the client SCSI adapter.
You can use this disk (hdisk20 physical, and known as mp1_hdisk5 on the client partitions) to create a diskgroup, a shared volume, and eventually a shared file system.
Perform regular VCS operations on the clients vis-a-vis service groups, resources, resource attributes, etc.