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100 lines
2.9 KiB
Plaintext
100 lines
2.9 KiB
Plaintext
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=head1 NAME
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fs_bypassthreshold - get/set Cache Bypass file size threshold
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=head1 SYNOPSIS
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=for html
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<div class="synopsis">
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B<fs bypassthreshold> S<<< [B<-size> <I<file size>>] >>> [B<-help>]
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B<fs bypassthresh> S<<< [B<-s> <I<file size>>] >>> [B<-h>]
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=for html
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</div>
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=head1 DESCRIPTION
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The B<fs bypassthreshold> command either changes the AFS client Cache
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Bypass file size threshold, or reports the current threshold. Normally,
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when an application tries to read data via the OpenAFS client, the client
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will fetch the required data from the fileserver, store the results in
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the local cache, and then serve the application request from the local
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cache. When the Cache Bypass feature is enabled, certain files will be
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read directly from the network, and the data will not be saved to the
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local cache. In some scenarios, this can provide a significant
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performance improvement, especially if the data is only read once.
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Currently, the only way to specify which files should bypass the cache
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and which files should not, is by file size. In the future, different
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mechanisms may exist for specifying which files should bypass the local
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cache and which should not.
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If B<-size> is not specified, B<fs bypassthreshold> just reports the
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current threshold and exits.
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=head1 CAUTIONS
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Cache Bypass is still considered an experimental feature. Even in stable
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releases of OpenAFS, it is not considered as stable as the rest of OpenAFS.
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=head1 OPTIONS
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=over 4
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=item B<-size> <I<file size>>
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Specifies how large a file must be in order to enable Cache Bypass mode.
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If a file is larger than the specified file size (in bytes), reading from
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that file will bypass the local cache and be read directly from the
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network. A file size of -1 indicates that Cache Bypass should be disabled
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complete, so no files will enable Cache Bypass mode, no matter how large
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they are.
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By default, Cache Bypass is disabled.
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=item B<-help>
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Prints the online help for this command. All other valid options are
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ignored.
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=back
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=head1 OUTPUT
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The output format is identical whether or not B<-size> was specified. If
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B<-size> is specified, the bypass threshold is changed, and the output
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represents the new, changed, threshold. Otherwise the output represents
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the current threshold.
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=head1 EXAMPLES
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The following example turns on Cache Bypass with a threshold of 4KiB:
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% fs bypassthreshold 4096
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Cache bypass threshold 4096
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The following example disables Cache Bypass:
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% fs bypassthreshold -1
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Cache bypass threshold -1 (disabled)
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The following example examines the current Cache Bypass threshold:
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% fs bypassthreshold
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Cache bypass threshold 4096
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=head1 PRIVILEGE REQUIRED
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To set the bypass threshold, the issuer must be logged in as the local
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superuser C<root>. Otherwise, no privilege is required.
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=head1 COPYRIGHT
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Copyright 2012 Sine Nomine Associates
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This documentation is covered by the BSD License as written in the
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doc/LICENSE file. This man page was written by Andrew Deason for
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OpenAFS.
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