From: Dave T. (davidlt77@hotmail.com)
Date: Wed May 21 2003 - 08:11:33 EDT
After I sent my previous summary, Bill Hassell provided some enlightening
information. I've included it below.
It turns out that the VG wasn't originally configured to handle more disks,
so we can't add any more. We are migrating to a VA, so we will allocate
more space to the VG before we begin migration.
Thanks for your help, Bill!
Dave
----Original Message Follows----
From: Bill Hassell <blhconsulting@mindspring.com>
To: "Dave T." <davidlt77@hotmail.com>
Subject: Re: RE: [HPADM] How to Move Some Free PE's to Another VG
Date: Tue, 20 May 2003 13:03:15 0200 (UTC)
Hi,
The document is accurate and works very well. However, it
states clearly at the beginning that this is used to move
extents around in a single volume group. For instance,
to improve performance, you might take a busy lvol and move
it to another PV (physical disk). But the disk must already
be part of the same volume group. pvmove is an atomic
operation which means that the system can be very busy and
the move will always work OK, albeit slowly since each move
is carefully monitored to ensure that the data is completely
intact and not changed during the move.
What I'm considering is moving PV's from vgpd to vgpd1. Although we have
a
lot of free PV's on vgpd, all those PV's currently have extents in use.
However, I want to try to do the following:
1. Move the data from some of the PV's to other PV's within vgpd using
pvmove.
2. Remove the free PV's from vgpd.
3. Add the free PV's to vgpd1.
The problem is that if you look at the pvmove command, there
is no option to specify a disk in another VG. It would make
no sense to do this since splitting \extents among different
VGs would mean that soime central location keeps track of all
the extents for all the disks and the purpose of a VG is no
longer valid.
Following are the contents of a document from the ITRC:
How to move logical volumes from one disk to another using pvmove DocId:
KBRC00003756 Updated: 9/29/00 5:26:00 AM
PROBLEM
This document explains how to move all the data on a LVM disk to a
different
disk in the same volume group.
Notice the "same volume group"?
So it isn't risky, it's impossible. Buy another disk or two.
NOTE: If the original VG was not created with enough extents
to handle additional disks, adding the disk will not give you
all the space. You are limited to 65k extents total. When you
first create a VG, the extent size is adjusted automatically
(larger than 4 megs) to accomodate all the disk that you add
to the VG. But if you add more disks later, the extent size
may be too small to count the new space and you *must* rebuild
the VG from scratch, which means backup the data, remove the VG,
then rebuild the VG and specify an override for the extent size
large enough to handle more disk in the future (ie, 16 or 32 meg
extents if the VG will grow to terabyte size).
Bill
--
Best regards,
Bill Hassell (blhconsulting@mindspring.com)
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