NAME

       globaliolimits.cfg - global I/O limiting configuration

DESCRIPTION

       The file globaliolimits.cfg contains configuration of the global I/O limiter.

SYNTAX

       Syntax is:

       option value

       Lines starting with # character are ignored.

OPTIONS

       Configuration options:

       subsystem <subsystem>
           The cgroups subsystem by which clients are classified. If left unspecified, all clients are
           considered unclassified (see below).

       limit unclassified <throughput in KiB/s>
           This is a special entry for clients that don’t match any group specified in configuration file or for
           all clients if subsystem 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.

       limit <group> <throughput in KiB/s>
           Set limit for clients belonging to the cgroups group <group>. In LizardFS, subgroups of <group>
           constitute independent groups; they are not allowed to use <group>'s bandwidth reservation and they
           don’t count against <group>'s usage.

EXAMPLES

           # empty file

       I/O limiting is disabled, no limits are enforced.

           limit unclassified 1024

       All clients are unclassified and share 1MiB/s of bandwidth.

           subsystem blkio
           limit /a 1024

       Clients in the blkio /a group are limited to 1MiB/s, no other clients can perform any I/O.

           subsystem blkio
           limit unclassified 256
           limit /a   1024
           limit /b/a 2048

       The blkio group /a is allowed to transfer 1MiB/s, while /b/a gets 2MiB/s. Clients from other groups (e.g.
       /b, /z, /a/a, /b/z) are considered unclassified and share 256KiB/s of bandwidth.

TUNING NOTES

       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.

       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)).

       Such reservation are wasted if the traffic at given mount instance suddenly drops.

       The ratio of bandwidth being wasted due to this phenomenon shouldn’t exceed fsp/b, where:

           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)

       This applies to each group separately, because groups reserve their bandwidth independently from each
       other.

COPYRIGHT

       Copyright 2008-2009 Gemius SA, 2013-2015 Skytechnology sp. z o.o.

       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.

       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.

       You should have received a copy of the GNU General Public License along with LizardFS. If not, see
       http://www.gnu.org/licenses/.

SEE ALSO

       mfsmaster.cfg(5)

                                                   01/19/2020                              GLOBALIOLIMITS.CFG(5)