FS_BYPASSTHRESHOLD(1) AFS Command Reference FS_BYPASSTHRESHOLD(1)NAMEfs_bypassthreshold - get/set Cache Bypass file size threshold
SYNOPSIS
fs bypassthreshold [-size <file size>] [-help]
fs bypassthresh [-s <file size>] [-h]
DESCRIPTION
The fs bypassthreshold command either changes the AFS client Cache
Bypass file size threshold, or reports the current threshold. Normally,
when an application tries to read data via the OpenAFS client, the
client will fetch the required data from the fileserver, store the
results in the local cache, and then serve the application request from
the local cache. When the Cache Bypass feature is enabled, certain
files will be read directly from the network, and the data will not be
saved to the local cache. In some scenarios, this can provide a
significant performance improvement, especially if the data is only
read once.
Currently, the only way to specify which files should bypass the cache
and which files should not, is by file size. In the future, different
mechanisms may exist for specifying which files should bypass the local
cache and which should not.
If -size is not specified, fs bypassthreshold just reports the current
threshold and exits.
CAUTIONS
Cache Bypass is still considered an experimental feature. Even in
stable releases of OpenAFS, it is not considered as stable as the rest
of OpenAFS.
OPTIONS-size <file size>
Specifies how large a file must be in order to enable Cache Bypass
mode. If a file is larger than the specified file size (in bytes),
reading from that file will bypass the local cache and be read
directly from the network. A file size of -1 indicates that Cache
Bypass should be disabled complete, so no files will enable Cache
Bypass mode, no matter how large they are.
By default, Cache Bypass is disabled.
-help
Prints the online help for this command. All other valid options
are ignored.
OUTPUT
The output format is identical whether or not -size was specified. If
-size is specified, the bypass threshold is changed, and the output
represents the new, changed, threshold. Otherwise the output represents
the current threshold.
EXAMPLES
The following example turns on Cache Bypass with a threshold of 4KiB:
% fs bypassthreshold 4096
Cache bypass threshold 4096
The following example disables Cache Bypass:
% fs bypassthreshold -1
Cache bypass threshold -1 (disabled)
The following example examines the current Cache Bypass threshold:
% fs bypassthreshold
Cache bypass threshold 4096
PRIVILEGE REQUIRED
To set the bypass threshold, the issuer must be logged in as the local
superuser "root". Otherwise, no privilege is required.
COPYRIGHT
Copyright 2012 Sine Nomine Associates
This documentation is covered by the BSD License as written in the
doc/LICENSE file. This man page was written by Andrew Deason for
OpenAFS.
OpenAFS 2013-10-09 FS_BYPASSTHRESHOLD(1)
