Re: hpux persistent device names

[varadharaj tamilvanan]

Dear Ganesh,

   There is nothing called Persistent Binding in HPUX OEM HBA since all HPUX system uses HPUX HBA drivers.

   As for the HDLM (Multipathing SW) I have installed on AIX Server which was already setup with Volume Groups. It just creates additional device files for the Physical Disks using the HDLM driver and won't disturb the existing devices and VG info.

 In order to use the multipath feature you need to import the new HDLM device files into Volume groups. It is just like the reconfiguration of Volume group that you do when there is a change in the HW address of the Physical volumes.

  Hope this helps.

 

Best Regards,

V.Tamilvanan

----- Original Message ----
From: Ganesan Sudalai <gane...@gmail.com>
To: storag...@googlegroups.com
Sent: Tuesday, January 9, 2007 6:23:05 AM
Subject: hpux persistent device names

Hi Folks,

 

How does persistent binding of FC device works in hpux

 

In case a LUN is bound on wwn level, how does the device will be looked in the OS?

Is it still Cxtxdx style or it comes as /dev/c20000xxxd0 something like that?

 

What does happen if you install new HDLM(Any multipathing SW) on these device to Volume group data?

 

If somebody can throw some light fast on this, it would be helpful :)

--
Cheers

Ganesh

Whatever the mind can conceive and believe, the mind can achieve.
~ Dr. Napoleon Hill

http://poigaiblog.blogspot.com/

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[Avinash Kumar]

Further, Not quite sure about HDLM but HP secure path creates a new device file for the physical disk after masking all the original disk device files, meaning when you say ioscan -fnC disk you will see only one path instead of 4 for an active/passive SAN, the path failover will be taken care by the multipathing sw.

 

Incase of an active/active controller, you will see all the path listed as active and you use one of the device path out of four to create VGs etc. The loadbalancing and path failover will be taken care by the multipathing sw.

 

In your case, since you have the VGs already created, I would take a vgexport for the VGs from SAN just as a precautionary.

 

I will install multipathing software.

 

I would check for the device file created by the multipathing software to confirm  multipathing sw is actually working.

 

if your multipathing sw masks the path, I will just rename the /etc/lvmtab to /etc/lvmtab.old, then I will do a vgscan. End of the story.

 

If your multipathing sw lists the old device paths including the new one, I will take a vgexport -p -m /tmp/vgsan.map -f /tmp/vgsan.pmap.

 

I will edit the vgsan.pmap for the multipathing sw's device path

 

do a vgexport and do a vgimport using the vgsan.pmap file

 

I assume that your disks are not mirrored at the host side.

 

Kind regards...Avi
 

[Ganesan Sudalai]

HI Guys,

 

Thx for the nputs. As tamil said, there should not be much problem generally. And the OS is 11.11 and i assume it should be Base VXVM and tht should make the things more better.

 

Also Whenever we load multipath SW like HDLM/Secure path, it creates a new path instead of the old Device names.

 

In general environment, it should not be a problem.

 

But the current situation is the device names are hard ported to have the same physical device name even after the reboot. SOmething like in Solaris, you get the device names of the hard disk such as /dev/c560xxxxxxxxd0.

 

So what would happen in this case? Has anybody come across such situations? And customer still want to keep the same kind of persistent binding even after HDLM.

 

Hope i am trying to make my problem more clear?

[Avinash Kumar]

Is it showing the device id like /dev/c560xxxxxxxxd0 for all paths ?

 

Please can you paste the "ioscan -fnC disk" output, also the output from your multipathing software that would say which paths are available/failed etc.

 

Kind regards...Avi
 

[Ganesan Sudalai]

I DOnt have the system available readily and can only do in another couple of days.

 

Also it does not have HDLM curently and has to be installed newly. Thats why i want to take more precaution :)