HP-UX System Administrator's Guide: Overview

• your system must be running HP-UX 11i Version 3 September 2008 Update, or
later
• sufficient swap space must remain active (following the change) to continue to
operate your system
Use the swapoff command to disable paging to a specific swap area. For example:
/usr/sbin/swapoff /dev/vg00/lvol2
Guidelines for Setting Up Swap Areas
There are some guidelines to consider when configuring swap space on your system.
Most of these are focused on maximizing the performance of HP-UX.
Device Swap Guidelines
Use the following guidelines to configure the most commonly used type of swap space,
device swap:
• Interleave device swap areas for better performance.
Two swap areas on different disks perform better than one swap area with the
equivalent amount of space. This allows interleaved swapping which means the
swap areas are written to concurrently, minimizing disk head movement, thus
enhancing performance.
When using LVM, you should set up secondary swap areas within logical volumes
that are on different disks (physical volumes) using lvextend.
If you have only one disk and need to increase swap space, try to move the primary
swap area to a larger region on the disk.
To see which devices are already being used for device swap use the command:
swapinfo -d
• Try to keep multiple device swap areas similar in size.
Device swap areas should have similar sizes for best performance. When you
configure swap areas of different sizes, when all space in the smaller device swap
area is used only the larger swap area is available making interleaving no longer
possible and slowing down paging performance.
• The nswapdev tunable system parameter controls the maximum number of swap
devices. Although the default value for nswapdev is large enough to accommodate
nearly all HP-UX systems, verify that it is large enough to accommodate the number
of swap areas you require.
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