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'\" t
.\" Title: vfs_preopen
.\" Author: [see the "AUTHOR" section]
.\" Generator: DocBook XSL Stylesheets v1.78.1 <http://docbook.sf.net/>
.\" Date: 02/21/2015
.\" Manual: System Administration tools
.\" Source: Samba 4.0
.\" Language: English
.\"
.TH "VFS_PREOPEN" "8" "02/21/2015" "Samba 4\&.0" "System Administration tools"
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.SH "NAME"
vfs_preopen \- Hide read latencies for applications reading numbered files
.SH "SYNOPSIS"
.HP \w'\ 'u
vfs objects = preopen
.SH "DESCRIPTION"
.PP
This VFS module is part of the
\fBsamba\fR(7)
suite\&.
.PP
This module assists applications that want to read numbered files in sequence with very strict latency requirements\&. One area where this happens in video streaming applications that want to read one file per frame\&.
.PP
When you use this module, a number of helper processes is started that speculatively open files and read a number of bytes to prime the file system cache, so that later on when the real application\*(Aqs request comes along, no disk access is necessary\&.
.PP
This module is stackable\&.
.SH "OPTIONS"
.PP
preopen:names = /pattern/
.RS 4
preopen:names specifies the file name pattern which should trigger the preopen helpers to do their work\&. We assume that the files are numbered incrementally\&. So if your file names are numbered FRAME00000\&.frm FRAME00001\&.frm and so on you would list them as
preopen:names=/FRAME*\&.frm/
.RE
.PP
preopen:num_bytes = BYTES
.RS 4
Specifies the number of bytes the helpers should speculatively read, defaults to 1\&.
.RE
.PP
preopen:helpers = NUM\-PROCS
.RS 4
Number of forked helper processes, defaults to 1\&.
.RE
.PP
preopen:queuelen = NUM\-FILES
.RS 4
Number of files that should be speculatively opened\&. Defaults to the 10 subsequent files\&.
.RE
.SH "VERSION"
.PP
This man page is correct for version 3\&.3 of the Samba suite\&.
.SH "AUTHOR"
.PP
The original Samba software and related utilities were created by Andrew Tridgell\&. Samba is now developed by the Samba Team as an Open Source project similar to the way the Linux kernel is developed\&.
.PP
The PREOPEN VFS module was created with contributions from Volker Lendecke and the developers at IBM\&.
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