topic Re: Split Root Volume Group and Boot in Operating System - HP-UX

Split Root Volume Group and Boot

Michael Ernstoff — Fri, 09 Sep 2005 10:47:41 GMT

I have an HP-UX 11i system with root volume group mirrored using Mirror-UX.
I split each lvol in the root volume group so that I have all the standard lvols on the disk which has the primary boot path, and all the split volumes on the disk which has the alternate boot path.
I checked each split lvol, by running fsck and then mounting under /altroot.
I edited /altroot/etc/fstab to use the alternate volumes.
I tried re-booting from the alternate path. I had hoped that it would use all the backed up lvols, but it used all the standard ones.
What do I need to do to ensure that I can choose which set of lvols gets used according to which disk I boot from?

I need to upgrade several servers. I will make a tape recovery as well, but a fast reboot would really help me in case I need to back out changes.

Re: Split Root Volume Group and Boot

Mel Burslan — Fri, 09 Sep 2005 11:01:45 GMT

The only way I know for sure to save a copy of the old OS just in case, is to yank the disk out of its slot and let the server boot from the disk standing alone on your system. Otherwise, it is not going to that simple to use a modified fstab file I am afraid. Also it is a good practice to power off (or yanking out) the other disk as the install process can detect this device if it is plugged in and may use it inadvertently.

Re: Split Root Volume Group and Boot

Sanjay_6 — Fri, 09 Sep 2005 11:05:45 GMT

Hi Michael,

Try this link from ITRC. The itrc doc id is KBRC00010661.

http://www1.itrc.hp.com/service/cki/docDisplay.do?docLocale=en_US&docId=200000080061911

Hope this helps.

Regds

Re: Split Root Volume Group and Boot

Geoff Wild — Fri, 09 Sep 2005 14:43:43 GMT

I found a way that this can be done - it is unsupported at HP.

It is a tedious process and the first time though it is somewhat difficult but if scripted it could be a fail safe way for us to recover servers during outages. Recovery time is the time it would take to reboot the server (about 10 minutes) as compared to the time to re-ignite (1 to 2 hours - depending on size of vg00 and sometimes doesn't work). The trick is to have two BDRAs and for this you need to take one of the disks out of the vg00, put it in a different VG (vgroot in this scenario) while making it a bootable copy of the primary disk. In short - you simply lvremove the split mirrors LVs, vgreduce the split mirror disk out of vg00, lvcreate the split mirrors into a different VG (this is achievable because the LV data is still on the split mirror disk), issue your lvlnboot commands against the split mirror VG, alter the fstab/lvmtab and with a couple other steps your there.

Example:

root@svr3003 /newroot/etc[187]> lvlnboot -v
Boot Definitions for Volume Group /dev/vg00
Physical Volumes belonging in Root Volume Group:
/dev/dsk/c2t2d0 (0/0/2/0.2.0) -- Boot Disk
Boot: lvol1b on: /dev/dsk/c2t2d0
Root: lvol3b on: /dev/dsk/c2t2d0
Swap: lvol2b on: /dev/dsk/c2t2d0
Dump: lvol2b on: /dev/dsk/c2t2d0, 0

Boot Definitions for Volume Group /dev/vgroot
Physical Volumes belonging in Root Volume Group:
/dev/dsk/c1t2d0 (0/0/1/1.2.0) -- Boot Disk
Boot: lvol1 on: /dev/dsk/c1t2d0
Root: lvol3 on: /dev/dsk/c1t2d0
Swap: lvol2 on: /dev/dsk/c1t2d0
Dump: lvol2 on: /dev/dsk/c1t2d0, 0

The svr3003 server is set to boot off both internal disks (/dev/dsk/c2t2d0 - /dev/dsk/c1t2d0) without any intervention other than issuing the setboot command or interrupting the boot sequence and booting from whichever disk.

Make sure you have an Ignite tape/network backup just in case!

Rgds...Geoff

Re: Split Root Volume Group and Boot

Michael Ernstoff — Sat, 10 Sep 2005 04:11:48 GMT

The link you gave is to the USA website.
As a user of the European site I cannot follow the link (why can't HP put us all in one support site?).
I tried searching by document ID on the Europe site but it does not find the document. Is there another way to find it?

Another option for me would be to find out if the changes worked or not, and then either lvmerge the volumes back, or remove the redundant volumes and re-mirror.
Are there any documents on the best way to achieve this?

Re: Split Root Volume Group and Boot

Devender Khatana — Sat, 10 Sep 2005 04:54:38 GMT

Hi Michael,

This document discuss both syncing and reverse syncing. Attached are the contents of the document as I was able to open it from India.

HTH,
Devender