From: Holger.VanKoll@SWISSCOM.COM
Date: Thu Nov 14 2002 - 06:06:05 EST
you can decreaste hd6, but you have to reboot
System Management Guide: Operating System and Devices
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Resizing or Moving the hd6 Paging Space
This article discusses various ways to modify the hd6 paging space. The
following procedures describe how to make the hd6 paging space smaller
and how to move the hd6 paging space within the same volume group. For a
discussion of recommended sizes of paging spaces, see "Placement and
Sizes of Paging Spaces" in AIX Versions 3.2 and 4 Performance Tuning
Guide.
System managers and users sometimes want to reduce the default paging
space in order to:
Enhance storage system performance by forcing paging and swapping to
other disks in the system that are less busy.
Conserve disk space on hdisk0.
Moving hd6 to a different disk is another way to enhance storage system
performance. Whether moving the paging space or reducing its size, the
rationale is the same: move paging space activity to disks that are less
busy. The installation default creates a paging logical volume (hd6) on
drive hdisk0, which contains part or all of the busy / (root) and /usr
file systems. If the minimum Inter Allocation policy is chosen, meaning
that all of / and a large amount of /usr are on hdisk0, moving the
paging space to a disk that is less busy should significantly improve
performance. Even if the maximum Inter Allocation policy is implemented
and both / and /usr are distributed across multiple physical volumes,
your hdisk2 (assuming three disks) would likely contain fewer logical
partitions belonging to the busiest file systems.
You can check your logical volume and file system distribution across
physical volumes by using the following command:
lspv -l hdiskX
Note: The steps in the following procedures are all necessary, even
those not directly related to the hd6 paging space. The additional steps
are needed because a paging space cannot be deactivated while the system
is running.
Prerequisites
Be sure to read the following articles before attempting to move a
paging space to a different disk:
Paging Space Overview
Managing Paging Spaces
Logical Volume Storage Overview
Making the hd6 Paging Space Smaller
Notes:
If you decide to reduce hd6, you must leave enough space for the
software in rootvg. A rule of thumb for reducing hd6 paging space is to
leave enough space to match physical memory. To find out the amount of
physical memory, use the following command:
lsattr -E -l sys0 -a realmem
AIX Version 4.2.1 and later does not support reducing the size of hd6
below 32MB or the system will not boot.
This procedure assumes that hd6 is on rootvg, which is located on
hdisk0. Create a temporary paging space for this procedure on rootvg as
follows:
mkps -a -n -s 20 rootvg
This command outputs the name of the paging space (paging00 if no others
exist).
Use the following command to deactivate the hd6 paging spaces in
preparation for the reboot later in the procedure:
chps -a n hd6
Change the paging space entry in the /sbin/rc.boot file from:
swapon /dev/hd6
to
swapon /dev/paging00
Change the primary dump device designation to be the paging space
paging00.
sysdumpdev -P -p /dev/paging00
Create a bootable image with the bosboot command for a hard disk image:
bosboot -d /dev/hdisk0 -a
Put the system key (if present) in the Normal position and use the
following command, which will both shut down the operating system and
reboot it:
shutdown -r
Remove the hd6 paging space:
rmps hd6
Create a new logical volume of the size you want for the hd6 paging
space:
mklv -t paging -y hd6 rootvg 10
Change the primary dump device designation back to be the paging space
hd6.
sysdumpdev -P -p /dev/hd6
Change the paging space entry in the /sbin/rc.boot file from:
swapon /dev/paging00
to
swapon /dev/hd6
Create a bootable image with the bosboot command for a hard disk image:
bosboot -d /dev/hdisk0 -a
Make the hd6 paging space available to the system:
swapon /dev/hd6
Change the temporary paging space, paging00, so that it does not
automatically activate at reboot time:
chps -a n paging00
Put the system key (if present) in the Normal position and use the
following command, which will both shut down the operating system and
reboot it:
shutdown -r
Remove the temporary paging space:
rmps paging00
Moving the hd6 Paging Space within the Same Volume Group
Note: Moving a paging space with the name hd6 from rootvg to another
volume group is not recommended because the name is hard-coded in
several places, including the second phase of the boot process and the
process that accesses the root volume group when booting from removable
media. Only the paging spaces in rootvg will be active during the second
phase of the boot process, and having no paging space in rootvg could
severely affect system boot performance. If you want the majority of
paging space on other volume groups, it is better to make hd6 as small
as possible (the same size as physical memory) and then create larger
paging spaces on other volume groups (see "Adding and Activating a
Paging Space").
Moving the default paging space from hdisk0 to a different disk within
the same volume group is a fairly simple procedure because you do not
have to shut down and reboot as in the other procedure in this article.
Use the following command to move the default (hd6) paging space from
hdisk0 to hdisk2:
migratepv -l hd6 hdisk0 hdisk2
-----Original Message-----
From: William Liu [mailto:borgliu@mail2000.com.tw]
Sent: Thursday, November 14, 2002 11:54 AM
To: aix-l@Princeton.EDU
Subject: reduce hd6(paging space) size
Hi! list:
Because my rootvg is not enough space , (only 9GB disk)
in the first, I set hd6(paging space ) to 2GB
now I want to reduce hd6 to 1GB
I add another paging space in another VG for 2GB
can I directly remove hd6 and re-create hd6 and set size to 1GB??
thanks.
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