AIX 6.1 TL7 introduced a new flag for the ‘lspv’ command which shows
the unique id (UUID) of disks in additional columns of the lspv
output.

This new ‘lspv -u’ is particularly useful in VIO environments using
VSCSI because the VIO client LPAR hdisk UDID contains the real UDID
from the VIO server hdisk.

For example on a client LPAR using VSCSI for the rootvg (merged
columns and spaces in the UDID are not a paste error):

Client LPAR # lspv -u
hdisk0          00000000fb8a0572                    rootvg          active      533E3E21360170E50202E5A5A0000025E50A12AB20F1746      FAStT03IBMfcp05VDASD03AIXvscsi8060a98a-0292-e2c9-0382-b5263f2a7e61

VIO1 # lspv -u
hdisk0          0000000017b33224                    rootvg          active              2A1135000C5005474B9C30BST9146853SS03IBMsas                          b98fed26-76da-f15c-45c9-b65a814e3d75
hdisk1          000000009c4ae1f9                    rootvg          active              2A1135000C500546FA9330BST9146853SS03IBMsas                          c3435ec2-3db2-6c0e-f14e-947243ba482d
hdisk2          000000000572fb8a                    None                                3E21360170E50202E5A5A0000025E50A12AB20F1746      FAStT03IBMfcp      a9be7b27-42fd-b0d6-a5ba-da61929cf4fc
hdisk3          0000000038963f05                    None                                3E21360170E50202E5A5A0000037350A526780F1746      FAStT03IBMfcp      7ed82295-3d9e-36dc-d6e9-e094d0d1a4ee

VIO2 # lspv -u
hdisk0          00000000b46edc87                    rootvg          active              2A1135000C5004CE6C7FF0BST9146853SS03IBMsas                          a36f5dae-8281-4df7-7fa7-e9fbf619c7d5
hdisk1          00000000605de1f9                    rootvg          active              2A1135000C5004CE6CF8F0BST9146853SS03IBMsas                          d1148dc8-ea98-a255-bf34-2921a56e8ca1
hdisk2          000000000572fb8a                    None                                3E21360170E50202E5A5A0000025E50A12AB20F1746      FAStT03IBMfcp      a9be7b27-42fd-b0d6-a5ba-da61929cf4fc
hdisk3          0000000038963f05                    None                                3E21360170E50202E5A5A0000037350A526780F1746      FAStT03IBMfcp      7ed82295-3d9e-36dc-d6e9-e094d0d1a4ee

Our client UDID contains the UDID from the VIO server with a prefix
and suffix:

client hdisk0: 533E3E21360170E50202E5A5A0000025E50A12AB20F1746      FAStT03IBMfcp05VDASD03AIXvscsi
vio1   hdisk2: ^^^^3E21360170E50202E5A5A0000025E50A12AB20F1746      FAStT03IBMfcp^^^^^^^^^^^^^^^^^

where ^ indicates the prefix and suffix added by the VIO server.

Using UDIDs the client can be cross referenced to the server quickly
with the most significant bytes of the UDID, in this case the middle
15 digits.

Historically to find the real LUN that a client is using in a VIO
environment would require the following steps for each VIO server:

– Obtain client hdisk parent vscsi device hardware location code and
LUN number
– Lookup on HMC which VIO server and slot the client vscsi device is
linked to
– Lookup vhost adapter on VIO server by slot number
– Lookup VSCSI mappings for vhost adapter to location hdisk on VIO server

A client with dual VIO would have to repeat the procedure twice. PVIDs
can also shortcut the process, but they may not show up on the VIO
server’s lspv output until after they are written to by the client and
the VIO server is rebooted. If the client rewrites the PVID, the VIO
server can also be out of date. Thus UDID’s are the preferred method
because they are static values.

The output can stretch the columns until they merge and spaces in the
UDID break the columns, which I hope is fixed in a future release.

——————————————————————
Russell Adams                            RLAdams@AdamsInfoServ.com

PGP Key ID:     0x1160DCB3           http://www.adamsinfoserv.com/

Fingerprint:    1723 D8CA 4280 1EC9 557F  66E8 1154 E018 1160 DCB3