topic Re: normal vgextend in Operating System - HP-UX

normal vgextend

DeafFrog — Tue, 18 Dec 2012 12:45:48 GMT

Hello Gurus ,

I did a vgextend , for a lun from netapps :

# vgextend /dev/vg01 /dev/disk/disk41
Current path "/dev/dsk/c5t0d3" is an alternate link, skip.
Current path "/dev/dsk/c7t0d3" is an alternate link, skip.
Current path "/dev/dsk/c9t0d3" is an alternate link, skip.
Current path "/dev/dsk/c12t0d3" is an alternate link, skip.
Current path "/dev/dsk/c14t0d3" is an alternate link, skip.
Current path "/dev/dsk/c16t0d3" is an alternate link, skip.
Current path "/dev/dsk/c18t0d3" is an alternate link, skip.
Volume group "/dev/vg01" has been successfully extended.
Volume Group configuration for /dev/vg01 has been saved in /etc/lvmconf/vg01.conf

The alternate link message shown above , does not belong to disk41 , rather to another disk27 , whick is allocated from different storage to vg01 :

# ioscan -m dsf /dev/disk/disk41
Persistent DSF           Legacy DSF(s)
========================================
/dev/disk/disk41         /dev/dsk/c25t0d1
                         /dev/dsk/c23t0d1
You have mail in /var/mail/root
# ioscan -m dsf /dev/rdisk/disk27
Persistent DSF           Legacy DSF(s)
========================================
/dev/rdisk/disk27        /dev/rdsk/c3t0d3
                         /dev/rdsk/c5t0d3
                         /dev/rdsk/c14t0d3
                         /dev/rdsk/c12t0d3
                         /dev/rdsk/c16t0d3
                         /dev/rdsk/c18t0d3
                         /dev/rdsk/c7t0d3
                         /dev/rdsk/c9t0d3

why my intution is telling me there could have been wrong going on somewhere , is it.

Regards,

Re: normal vgextend

Torsten. — Tue, 18 Dec 2012 12:52:14 GMT

disk27 has 8 links, disk41 has only 2 - I assume zoning is correct, so you probably did not present the LUN to all available paths.

Compare the settings for both LUNs on the storage side.

Re: normal vgextend

Matti_Kurkela — Tue, 18 Dec 2012 14:16:58 GMT

When you are making changes to a VG that contains alternate links, you may see the "current path ... is alternate link, skip" messages that are not related to the PV you're adding/removing. I think this is because the VG configuration tools will validate the configuration of the entire VG whenever changes are made.

But... should you be seeing any "alternate link" messages at all on a properly-configured HP-UX 11.31?

Unless there is a specific reason to do otherwise, I think you should generally use Agile devices instead of legacy ones in VG configuration wherever possible.

Please run "lvmadm -l" to see all your VGs and their associated PVs. (This is the proper 11.31 replacement for the old "strings /etc/lvmtab" trick.)

Agile paths will eliminate the need to specify alternate paths (as each agile path will encompass all possible paths for a given disk/LUN) and will enable HP-UX to automatically load-balance between the paths, if the storage system allows that.

If you have legacy /dev/dsk PV paths included in any of your VG configurations, make sure you have a good reason for that - and make sure that all the PVs in that VG are using the same kind of paths. While mixing up legacy and agile paths within a single VG is possible and should not be harmful, doing it long-term is not good administration style.

Re: normal vgextend

Torsten. — Tue, 18 Dec 2012 14:20:25 GMT

Agreed, but multipathing should even work with the old device files.

However, the number of alternate paths in this case indicate a problem with presentation, right?

If the LUN is presented from the same storage device, it should have the same number of paths.