NAME
remote_nfs_swap — enable swapping across NFS
VALUES
Allowed values
0 (off)
or 1 (on)
DESCRIPTION
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?
Anyone.
Restrictions on Changing
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?
None.
WARNINGS
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
http://docs.hp.com.
AUTHOR
remote_nfs_swap
was developed by HP.
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