Tunable Kernel Parameters
NAME [Toc] [Back]
remote_nfs_swap - enable swapping across NFS
VALUES [Toc] [Back]
Allowed values [Toc] [Back]
0 (off) or 1 (on)
DESCRIPTION [Toc] [Back]
This tunable controls adding a NFS filesystem for use as swap. If
remote_nfs_swap is set to 0 (off), only local filesystems and devices
can be used for swap. If it is set to 1 (on), both local and
networked file systems can be used for swap.
Historically, this tunable was used in NFS clusters that are no longer
supported, but this capability has not yet been removed.
Who Is Expected to Change This Tunable?
Restrictions on Changing [Toc] [Back]
Changes to this tunable take effect on the next boot.
When Should the Tunable Be Turned On?
Almost never. As previously mentioned, this tunable was designed for
systems which are not in use today. Only systems with extremely
robust NFS capabilities should even consider using NFS for swap.
What Are the Side Effects of Turning the Tunable On?
If the value is set to 1 (on), and a NFS partition is added as swap,
then some kernel memory will be set aside for NFS transactions to the
swap file system. The kernel will then use the NFS swap partition
just the same as a local file system. If the NFS capabilities of the
system are not robust, this could lead to extremely long swap times
(both swap in and swap out), and possibly a loss of memory because all
the reserved memory and more could be used by NFS (just when memory
pressure is high) causing the need for swap.
When Should the Tunable Be Turned Off?
Unless you are positive that the NFS system can handle the load of
being used as swap, and does not have a local file system or disk
drive to spare, this tunable should always be set to 0 (off).
What Are the Side Effects of Turning the Tunable Off?
Any previously defined NFS swap filesystems will no longer be allowed.
Kernel memory will not be reserved for NFS transactions due to swap.
What Other Tunables Should Be Changed at the Same Time?
Hewlett-Packard Company - 1 - HP-UX 11i Version 2: Sep 2004
Tunable Kernel Parameters
WARNINGS [Toc] [Back]
All HP-UX kernel tunable parameters are release specific. This
parameter may be removed or have its meaning changed in future
releases of HP-UX.
Installation of optional kernel software, from HP or other vendors,
may cause changes to tunable parameter values. After installation,
some tunable parameters may no longer be at the default or recommended
values. For information about the effects of installation on tunable
values, consult the documentation for the kernel software being
installed. For information about optional kernel software that was
factory installed on your system, see HP-UX Release Notes at
AUTHOR [Toc] [Back]
remote_nfs_swap was developed by HP.
Hewlett-Packard Company - 2 - HP-UX 11i Version 2: Sep 2004 [ Back ]