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man lvmcache: add more writecache cachesettings info

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This commit is contained in:
David Teigland 2022-02-16 15:21:09 -06:00
parent d4a0816a58
commit ec2119bedd
1 changed files with 39 additions and 12 deletions
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51
man/lvmcache.7_main
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@ -243,15 +243,40 @@ can be used.
.
.SS dm-writecache settings
.
Tunable parameters can be passed to the dm-writecache kernel module using
the --cachesettings option when caching is started, e.g.
To specify dm-writecache tunable settings on the command line, use:
.br
--cachesettings 'option=N' or
.br
--cachesettings 'option1=N option2=N ...'
.P
For example, --cachesettings 'high_watermark=90 writeback_jobs=4'.
.P
To include settings when caching is started, run:
.P
.nf
# lvconvert --type writecache --cachevol fast \\
--cachesettings 'high_watermark=N writeback_jobs=N' vg/main
--cachesettings 'option=N' vg/main
.fi
.P
Tunable options are:
To change settings for an existing writecache, run:
.P
.nf
# lvchange --cachesettings 'option=N' vg/main
.fi
.P
To clear all settings that have been applied, run:
.P
.nf
# lvchange --cachesettings '' vg/main
.fi
.P
To view the settings that are applied to a writecache LV, run:
.P
.nf
# lvs -o cachesettings vg/main
.fi
.P
Tunable settings are:
.
.TP
high_watermark = <percent>
@ -301,11 +326,14 @@ writecache. Adding cleaner=0 to the splitcache command will skip the
cleaner mode, and any required flushing is performed in device suspend.
.SS dm-writecache using metadata profiles
Writecache allows to set a variety of options. Lots of these settings
can be specified in lvm.conf or profile settings. You can prepare
a number of different profiles in the \fI#DEFAULT_SYS_DIR#/profile\fP directory
and just specify the metadata profile file name when writecaching LV.
.
In addition to specifying writecache settings on the command line, they
can also be set in lvm.conf, or in a profile file, using the
allocation/cache_settings/writecache config structure shown below.
.P
It's possible to prepare a number of different profile files in the
\fI#DEFAULT_SYS_DIR#/profile\fP directory and specify the file name
of the profile when starting writecache.
.P
.I Example
.nf
@ -327,11 +355,10 @@ writeback_jobs=1024
EOF
.P
# lvcreate -an -L10G --name wcache vg /dev/fast_ssd
# lvcreate --type writecache -L10G --name main --cachevol wcache \\
# lvcreate -an -L10G --name fast vg /dev/fast_ssd
# lvcreate --type writecache -L10G --name main --cachevol fast \\
--metadataprofile cache_writecache vg /dev/slow_hdd
.fi
.
.SS dm-cache with separate data and metadata LVs
.