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Re: [linux-lvm] How to read internal physical volume number.

On Tue, May 15, 2001 at 07:06:23PM -0600, Steve Cranage wrote:
> I have a configuration with multiple paths to each pv, and need to sort
> them out so I know which device names are alternate paths to the same
> physical device. I had planned on using the internal serial number
> written to the pv's  when a pvcreate is done.

I assume you mean the PV number here which actually sits in the 4th filed
of the pvdisplay output.

For eg.
/dev/sdb1:vg00:8883882:1:1:2:1:4096:1084:0:1084:VYJ317-t4in-pYv9-eHnu-*                   ^^^^         ^


          ^^^^         ^

Because the second field tells you, that both PVs belong to the same VG (named
"vg00" in this example) you can figure out that /dev/sdb1 points to the PV
with internal number 1 and /dev/sdc1 points to PV #2.

You can even use the last field of the " pvdisplay -c" output to
base your search on PV UUIDs.

BTW: the library function pv_read_all_pv_of_vg() which is used to read in
     the PV metadata for the VG sorts out multiple access pathes today.
     This will change in a future LVM version which will support multi pathing.

> The man pages for pvdisplay seem to indicate this is in the 4th field of
> the output with the -c option, but alas, the -c option appears to not be
> coded as it doesn't affect the output of the pvdisplay command.

It should be (see my above example output).
But you pointed me to a lack in the manual page. The 12th field (the PV UUID)
wasn't discribed. Fixed it. Thanks.

> How else
> can I get the internal serial number?

pvscan -u

plus some shell/perl magic .

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Heinz    -- The LVM Guy --

*** Software bugs are stupid.
    Nevertheless it needs not so stupid people to solve them ***


Heinz Mauelshagen                                 Sistina Software Inc.
Senior Consultant/Developer                       Am Sonnenhang 11
                                                  56242 Marienrachdorf
Mauelshagen Sistina com                           +49 2626 141200
                                                       FAX 924446

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