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DescriptionJonathan Earl Brassow
2016-03-29 23:21:02 UTC
+++ This bug was initially created as a clone of Bug #1322162 +++
SMQ is the default in 7.2 (and 6.8), I believe.
Comment 2Jonathan Earl Brassow
2017-10-13 21:37:40 UTC
this is already fixed... although, the man page is overly verbose about the older MQ policy. I think we'd rather people simply used the default SMQ. This output is from 6.9.
Cache policy
The cache subsystem has additional per-LV parameters: the cache policy
to use, and possibly tunable parameters for the cache policy. Three
policies are currently available: "smq" is the default policy, "mq" is
an older implementation, and "cleaner" is used to force the cache to
write back (flush) all cached writes to the origin LV.
The "mq" policy has a number of tunable parameters. The defaults are
chosen to be suitable for the majority of systems, but in special cir-
cumstances, changing the settings can improve performance.
With the --cachepolicy and --cachesettings options, the cache policy
and settings can be set when creating a cache LV, or changed on an
existing cache LV (both options can be used together). The current
cache policy and settings of a cache LV can be displayed with the
cache_policy and cache_settings reporting options:
lvs -o+cache_policy,cache_settings VG/CacheLV
Example
Change the cache policy and settings of an existing cache LV.
# lvchange --cachepolicy mq --cachesettings \
'migration_threshold=2048 random_threshold=4' vg/lv1
lvm.conf(5) allocation/cache_policy
defines the default cache policy.