'\" t
.\"     Title: vfs_preopen
.\"    Author: [see the "AUTHOR" section]
.\" Generator: DocBook XSL Stylesheets v1.79.1 <http://docbook.sf.net/>
.\"      Date: 06/20/2019
.\"    Manual: System Administration tools
.\"    Source: Samba 4.9.5-Debian
.\"  Language: English
.\"
.TH "VFS_PREOPEN" "8" "06/20/2019" "Samba 4\&.9\&.5\-Debian" "System Administration tools"
.\" -----------------------------------------------------------------
.\" * Define some portability stuff
.\" -----------------------------------------------------------------
.\" ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
.\" http://bugs.debian.org/507673
.\" http://lists.gnu.org/archive/html/groff/2009-02/msg00013.html
.\" ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
.ie \n(.g .ds Aq \(aq
.el       .ds Aq '
.\" -----------------------------------------------------------------
.\" * set default formatting
.\" -----------------------------------------------------------------
.\" disable hyphenation
.nh
.\" disable justification (adjust text to left margin only)
.ad l
.\" -----------------------------------------------------------------
.\" * MAIN CONTENT STARTS HERE *
.\" -----------------------------------------------------------------
.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 part of version 4\&.9\&.5\-Debian 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\&.