Tag: lsattr

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Changing the PVID of a Physical Volume

Each physical volume used by AIX LVM has a unique physical volume ID, or PVID for short. The PVID is a software-generated ID that is stored in the header area of a disk (block 0). When a new disk is added to an AIX system, the new physical volume does not yet have a PVID. As soon as a physical volume is added to a volume group, a PVID is automatically generated if the physical volume should not already have a PVID. An already existing PVID is adopted.

A PVID can also be created manually, using the chdev command. The pv attribute is set to the value yes:

# chdev -l hdisk3 -a pv=yes
hdisk3 changed
#

The set PVID can be displayed either with the lsattr command or simply with lspv:

$ lsattr -El hdisk3 -a pvid -F value
00c276b0084049750000000000000000
$
$ lspv |grep hdisk3
hdisk3          00c276b008404975                    None                       
$

A PVID can also be removed again. However, the physical volume must not be in use for this (e.g. as part of a volume group).

To clear a PVID of a physical volume, the pv attribute can be set to the value clear:

# chdev -l hdisk3 -a pv=clear
hdisk3 changed
#

The PVID has been removed as shown by the following outputs:

$ lsattr -El hdisk3 -a pvid -F value
none
$
$ lspv |grep hdisk3
hdisk3          none                                None                       
$

Attempting to delete the PVID of a physical volume that is in use, results in the following error message:

# chdev -l hdisk0 -a pv=clear
Method error (/usr/lib/methods/chgdisk):
        0514-062 Cannot perform the requested function because the
                 specified device is busy.
     pv    

#
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The “label” Attribute for FC Adapters

As of AIX 7.2 TL4 and VIOS 3.1.1.10 there is a new attribute “label” for physical FC adapters. The administrator can set this attribute to any character string (maximum 255 characters). Even if the attribute is only informative, it can be extremely useful in PowerVM virtualization environments. If you have a large number of managed systems, it is not always clear to which FC fabric a certain FC port is connected. This can of course be looked up in the documentation of your systems, but it does involve a certain amount of effort. It is easier if you link this information directly with the FC adapters, which is exactly what the new “label” attribute allows in a simple way. On AIX:

# chdev -l fcs0 -U -a label="Fabric_1"
fcs0 changed
# lsattr -El fcs0 -a label -F value
Fabric_1
#

On virtual I/O servers, the attribute can also be set using the padmin account:

/home/padmin> chdev -dev fcs1 -attr label="Fabric_2" -perm
fcs1 changed
/home/padmin> lsdev -dev fcs1 -attr label                
value

Fabric_2
/home/padmin>

The attribute is also defined for older FC adapters.

If the “label” attribute is consistently used, it is always possible to determine online for each FC adapter to which fabric the adapter is connected to. This information only needs to be stored once for each FC adapter.

(Note: The “label” attribute is not implemented for AIX 7.1, at least not until 7.1 TL5 SP6.)