'\" t
.\"     Title: globaliolimits.cfg
.\"    Author: [FIXME: author] [see http://docbook.sf.net/el/author]
.\" Generator: DocBook XSL Stylesheets v1.79.1 <http://docbook.sf.net/>
.\"      Date: 06/17/2017
.\"    Manual: \ \&
.\"    Source: \ \&
.\"  Language: English
.\"
.TH "GLOBALIOLIMITS\&.CFG" "5" "06/17/2017" "\ \&" "\ \&"
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.SH "NAME"
globaliolimits.cfg \- global I/O limiting configuration
.SH "DESCRIPTION"
.sp
The file \fBglobaliolimits\&.cfg\fR contains configuration of the global I/O limiter\&.
.SH "SYNTAX"
.sp
Syntax is:
.sp
\fIoption\fR \fIvalue\fR
.sp
Lines starting with \fB#\fR character are ignored\&.
.SH "OPTIONS"
.sp
Configuration options:
.PP
\fBsubsystem <subsystem>\fR
.RS 4
The cgroups subsystem by which clients are classified\&. If left unspecified, all clients are considered
\fIunclassified\fR
(see below)\&.
.RE
.PP
\fBlimit unclassified <throughput in KiB/s>\fR
.RS 4
This is a special entry for clients that don\(cqt match any group specified in configuration file or for all clients if
\fBsubsystem\fR
is unspecified\&. If this entry is unspecified and subsystem is unspecified as well, I/O limiting is disabled entirely\&. If this entry is unspecified but subsystem is specified, unclassified clients are not allowed to perform I/O\&.
.RE
.PP
\fBlimit <group> <throughput in KiB/s>\fR
.RS 4
Set limit for clients belonging to the cgroups group
\fB<group>\fR\&. In LizardFS, subgroups of
\fB<group>\fR
constitute independent groups; they are not allowed to use
\fB<group>\*(Aqs\fR
bandwidth reservation and they don\(cqt count against
\fB<group>\*(Aqs\fR
usage\&.
.RE
.SH "EXAMPLES"
.sp
.if n \{\
.RS 4
.\}
.nf
# empty file
.fi
.if n \{\
.RE
.\}
.sp
I/O limiting is disabled, no limits are enforced\&.
.sp
.if n \{\
.RS 4
.\}
.nf
limit unclassified 1024
.fi
.if n \{\
.RE
.\}
.sp
All clients are \fIunclassified\fR and share 1MiB/s of bandwidth\&.
.sp
.if n \{\
.RS 4
.\}
.nf
subsystem blkio
limit /a 1024
.fi
.if n \{\
.RE
.\}
.sp
Clients in the \fBblkio\fR \fB/a\fR group are limited to 1MiB/s, no other clients can perform any I/O\&.
.sp
.if n \{\
.RS 4
.\}
.nf
subsystem blkio
limit unclassified 256
limit /a   1024
limit /b/a 2048
.fi
.if n \{\
.RE
.\}
.sp
The \fBblkio\fR group \fB/a\fR is allowed to transfer 1MiB/s, while \fB/b/a\fR gets 2MiB/s\&. Clients from other groups (e\&.g\&. \fB/b\fR, \fB/z\fR, \fB/a/a\fR, \fB/b/z\fR) are considered \fIunclassified\fR and share 256KiB/s of bandwidth\&.
.SH "TUNING NOTES"
.sp
Global I/O limiting is managed by the master server\&. Mount instances reserve bandwidth allocations from master when they want to perform I/O to chunkservers\&.
.sp
To avoid overloading the master under heavy traffic, mounts try to predict their future usage and reserve at once all the bandwidth they will for the next renegotiation period (see mfsmaster\&.cfg(5))\&.
.sp
Such reservation are wasted if the traffic at given mount instance suddenly drops\&.
.sp
The ratio of bandwidth being wasted due to this phenomenon shouldn\(cqt exceed \fBfsp/b\fR, where:
.sp
.if n \{\
.RS 4
.\}
.nf
f is the frequency of sudden traffic drops in the whole installation (in 1/s)
s is the average size of such drop (in KiB/s)
p is the renegotiation period (in s)
b is the bandwidth limit (in KiB/s)
.fi
.if n \{\
.RE
.\}
.sp
This applies to each group separately, because groups reserve their bandwidth independently from each other\&.
.SH "COPYRIGHT"
.sp
Copyright 2008\-2009 Gemius SA, 2013\-2015 Skytechnology sp\&. z o\&.o\&.
.sp
LizardFS is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, version 3\&.
.sp
LizardFS is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE\&. See the GNU General Public License for more details\&.
.sp
You should have received a copy of the GNU General Public License along with LizardFS\&. If not, see http://www\&.gnu\&.org/licenses/\&.
.SH "SEE ALSO"
.sp
mfsmaster\&.cfg(5)