hdisks and pdisks

hdisks and pdisks

Post by Ralf Wink » Fri, 16 Oct 1998 04:00:00


I am not familiar with SSA but I think the hdisk device is available
before it bekomes a physical disk to the system. The IBM online
dokumentation says:

        To change an available disk to a physical volume, enter:

        chdev -l hdisk3 -a pv=yes

        This causes the available disk (hdisk3 ) to be assigned a
        physical volume identifier (PVID) if it does
        not already have one.

Now you can put it into a volume group.


>I have an H50 that has some SSA disks on it
>that were moved from another machine.
>I believe they were part of an SSA RAID5 array.
>No exportvg, reducevg, etc were done on them
>prior to moving.  Also on this machine I've just
>done a fresh install of 4.3.1 (a 'fluid' environment, no?)
>so only rootvg is defined.

>The problem is I cannot get the machine to assign
>an hdisk to the pdisk.  The only thing that I've tried
>that works is to format the pdisk.  Then I can assign
>an hdisk to it and use the drive.  Is there an easier
>way or do I have to format the disk?

>Gordon Cerswell

Ralf Winkel                     |
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1. What's the difference between a pdisk and hdisk


Following AIX LVM terminology a VG is a collection of disks. A disk or
PV is represented by hdiskx. For example, hdisk0 is typically the disk
in rootvg. So what then is a pdisk or physical disk?

Carrying out the following commands only serves to confuse the issue:

# lscfg -vp pdisk0 | grep pdisk0
# pdisk0            00-05-P           4GB SSA C Physical Disk Drive

# lscfg -vp hdisk0 | grep hdisk0
# hdisk0            00-07-A1-3,0      2.2 GB 16 Bit SCSI Disk Drive

With thanks.

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