topic volume group has one disk using legacy pv name in Operating System - HP-UX

volume group has one disk using legacy pv name

PamelaJThrasher — Wed, 10 Jun 2009 18:39:17 GMT

Hello-
I have been gathering disk data on my 11.31 servers and found something odd in vg01 on two of them.

When I do a vgdisplay -v vg01 | grep "PV Name", I get the following:

PV Name /dev/dsk/c5t7d4
PV Name /dev/dsk/c7t7d4 Alternate Link
PV Name /dev/dsk/c9t7d4 Alternate Link
PV Name /dev/dsk/c11t7d4 Alternate Link
PV Name /dev/dsk/c13t7d4 Alternate Link
PV Name /dev/dsk/c15t7d4 Alternate Link
PV Name /dev/dsk/c19t7d4 Alternate Link
PV Name /dev/dsk/c17t7d4 Alternate Link
PV Name /dev/disk/disk1614
PV Name /dev/disk/disk3478

I have two questions about this:
1. Why would one of the disks be using the legacy naming convention while the others are using agile names? (as in how the heck could this have happened?)

2. How do I fix it so this one disk also uses its agile name?

Re: volume group has one disk using legacy pv name

melvyn burnard — Wed, 10 Jun 2009 18:49:53 GMT

Was the server upgraded from 11.23? And then some PV's added to the VG?
That would cause this
You could also do a strings /etc/lvmtab and compare what you see.
There is a command called vgdfs that may assist you here, I know that it converst what is in the lvmtab file to the new DSF format

Re: volume group has one disk using legacy pv name

Md. Minhaz Khan — Thu, 11 Jun 2009 08:28:37 GMT

>>as in how the heck could this have happened?)

You can confirm this by executing

#ioscan -m dsf /dev/disk/disk1614

and see what is the dsf corresponding address for that.

Thanks
Minhaz

Re: volume group has one disk using legacy pv name

Md. Minhaz Khan — Thu, 11 Jun 2009 08:33:34 GMT

Dear Thrasher,

I hope below information will help you.

As of HP-UX 11i Version 3, disk devices can be represented by two different types of device files in the /dev directory, legacy and persistent.

Legacy device files (DSF) were the only type of mass storage device files in releases prior to HP-UX 11i Version 3. They have hardware path information such as SCSI bus, target, and LUN encoded in the device file name and minor number. For example, the legacy device file /dev/dsk/c3t2d0 represents the disk at card instance 3, target address 2, and lun address 0.

Persistent device files(PDSF) are not tied to the physical hardware path to a disk, but instead map to the disk's unique worldwide identifier (WWID). Thus, the device file is unchanged if the disk is moved from one interface to another, moved from one switch or hub port to another, or presented from a different target port to the host. The name of a persistent device file follows a simpler naming convention: /dev/disk/diskn, where n is the instance number assigned to the disk. Neither the device file name nor the minor number contain any hardware path information.

In addition, if the disk has multiple hardware paths, it is represented by a single persistent device file. Persistent device files transparently handle multipathed disks and supersede LVM's multipathing functionality. If a disk has multiple hardware paths, which LVM refers to as pvlinks, the persistent device special file acts as a single access point for all the links. I/O requests are distributed across all available links by the mass storage stack, with a choice of load balancing algorithms. If a link fails, the mass storage stack automatically disables the failed link and I/O continues on all remaining links. Any failed or nonresponsive links are monitored, so that when a failed link recovers, it is automatically and transparently reincorporated into any load balancing. New disks and links are also automatically discovered and added to load balancing. If the disk's connectivity changesâ addition, removal, or modification of a linkâ applications using the persistent device file are not affected, provided at least one link is still active. New disks are automatically discovered

Thanks
Minhaz

Re: volume group has one disk using legacy pv name

sujit kumar singh — Thu, 11 Jun 2009 10:24:07 GMT

Hi

Please do the following:
#ioscan -kfnCdisk
#ioscan -kfNnCdisk
#ioscan -m dsf

find the corresponding agile DSFs for the legacy /dev/dsk/c5t7d4

#insf -eCdisk
#ioscan -m dsf

to check if te Persistent DSF gets created.

You can also use the vgscan to create the Definition of /dev/vg01

#vgscan -N -f /dev/vg01

-N shall put the entries of Persisitent DSFs for /dev/vg01 in /etc/lvmtab

-f is for asking the LVM to only scan for the /dev/vg01.

regards
sujit

Re: volume group has one disk using legacy pv name

PamelaJThrasher — Thu, 11 Jun 2009 10:48:51 GMT

Sujit-
Can I do the vgscan -N -f /dev/vg01 commnand while everything is up and running on the server without impacting anything?

Re: volume group has one disk using legacy pv name

sujit kumar singh — Thu, 11 Jun 2009 11:21:35 GMT

Hi

please refer pages 23- 25 of this Doc.

http://h20000.www2.hp.com/bc/docs/support/SupportManual/c01919369/c01919369.pdf (BSC link updated by admin)

I can site a PDF describing that.
Logic says that yes you can do that -- suggest if you have 11iv3 2008 release and latest patches for LVM.

vgscan actually does the read of the disks so as to create LVMTAB that is /etc/lvmtab.
vgscan runs on a boot-time unless other wise specified maually to scan disks for VG membership and VG Quorum requirements and keeps that information and that is updated when a VG conf change like addition /deletion of PVs from Vgs or addition/removal of VGs takes place.

In my opinion you can do that Online with the applications running provided you are not in the middle of VG config changes.

But I am not too sure if the production is critical and still you can afford a downtime.

choice is i shall say yours, you can to be on a safer side plan this with a downtime assuming that right now you do not have any other issue with the /dev/vg01 apart from this.

regards
sujit

Re: volume group has one disk using legacy pv name

PamelaJThrasher — Thu, 11 Jun 2009 11:24:14 GMT

Thank you.