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Activating volume group takes long time

 
Christoph Ernst_2
Occasional Advisor

Activating volume group takes long time

Hello,
i have a problem with my volume groups on my two node mc service guard cluster.
The nodes are connected to a EMC SAN. Last week, the SAN has changed from a symmetrix to a clarion system. We got additional disk space, so i extended our volume groups. We have five volume groups, each has roundabout 1 TB. We have JFS, so i used fsadm to increase the size of my filesystems.
Since that modifications, activation of the volume groups take very long.
When i do a vgchange -a r /dev/vgxx, it takes roundabout 5 minutes until a vg is activated. When i deactivate a volume group and activate it again, its fast, until the next reboot of the server. After the reboot, activation takes 5 minutes per vg again.
My OS is HP-UX 11.23.
Does anybody has an idea what the problem could be.

Many thanks for your help!
Christoph
5 REPLIES 5
RAC_1
Honored Contributor

Re: Activating volume group takes long time

Are you up to date with patches?? Particlarly LVM patches??
There is no substitute to HARDWORK
Matti_Kurkela
Honored Contributor

Re: Activating volume group takes long time

I haven't had any chance to play with 11.23 yet, but this sounds like a problem with multipathing.

Check your volume groups with "vgdisplay -v ". Look at the physical volumes. If there are alternate paths listed with the PVs, check that all paths are up to date.

(Last time we did a SAN migration, one common mistake was forgetting to remove all the old disconnected paths from the configuration. No damage, but cleaning things up took a while.)

If there are several paths to a PV and the first listed path is not connected, the LVM system will switch to an alternate path after a while. From that point on until next reboot, it remembers that one path is down and prefers the working ones. If there are a lot of PVs in a volume group, the activation may indeed take a while.
MK
Christoph Ernst_2
Occasional Advisor

Re: Activating volume group takes long time

I used hp's patch assesment tool make the system up to date with patches.
There are alternate paths visible to the system, but they are not configured into the volume groups, because we have host based mirrors.
Bill Costigan
Honored Contributor

Re: Activating volume group takes long time

The clariion doesn't do alternate paths like the symmetrix. With the Clariion only one controller owns a LUN you can see the LUN through the other controller path but cannot access it. If you have powerpath installed it will switch the ownership of the LUN to the other controller when you try to access it through that path.

It sounds like the path [device file]you have in the vg is not the default owner as configured in powerpath. When you activate the vg and it tries to access the LUN through the path defined in the VG, powerpath has to flip the ownership of that LUN which takes a little time.

The second time you active the vg all the ownerships are already correct. When you reboot and restart powerpath all the ownership revert back to the default state.

At least that's my guess.

try the command 'powermt display all' before activating the VG and then compare the active paths to the ones in the vg.
Christoph Ernst_2
Occasional Advisor

Re: Activating volume group takes long time

Removing Patch 4.31 from EMC Power Path Software solved my problem.

Thank you all for your help.