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man: lvmcache better cache mode info and other command variations

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This commit is contained in:
David Teigland
2014-08-26 16:40:47 -05:00
parent 17ab39f743
commit 91198ac13e
1 changed files with 42 additions and 7 deletions
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49
man/lvmcache.7.in
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@ -214,16 +214,27 @@ pool sub-LVs redundant.
# lvconvert \-\-type cache \-\-cachepool vg/cache1 vg/lv1
.fi
.SS Writethough caching
.SS Cache mode
\&
Writethrough caching ensures that any data written will be stored both in
the cache pool LV and on the origin LV. The loss of a device associated
with the cache pool LV in this case would not mean the loss of any data.
When combining the cache data LV and the cache metadata LV to form the
cache pool LV, properties of the cache can be specified - in this case,
\fIwritethrough\fP vs. \fIwriteback\fP.
The default cache mode is "writethrough". Writethrough ensures that any
data written will be stored both in the cache pool LV and on the origin
LV. The loss of a device associated with the cache pool LV in this case
would not mean the loss of any data.
A second cache mode is "writeback". Writeback delays writing data blocks
from the cache pool back to the origin LV. This mode will increase
performance, but the loss of a device associated with the cache pool LV
can result in lost data.
The cache mode can be specified with the --cachemode option when a cache
pool LV is created.
.BR lvm.conf (5)
.B cache_pool_cachemode
.br
defines the default cache mode.
.nf
0. Create an origin LV we wish to cache (yours may already exist)
@ -264,6 +275,30 @@ the same VG.
.br
.B lvconvert --type cache\-pool VG/CacheDataLV
.SS Create a new cache LV without an existing origin LV
\&
A cache LV can be created using an existing cache pool without an existing
origin LV. A new origin LV is created and linked to the cache pool in a
single step.
.B lvcreate \-\-type cache \-L LargeSize \-n CacheLV
.RS
.B \-\-cachepool VG/CachePoolLV SlowPVs
.RE
.SS Single step cache pool LV creation
\&
A cache pool LV can be created with a single lvcreate command, rather than
using lvconvert on existing LVs. This one command creates a cache data
LV, a cache metadata LV, and combines the two into a cache pool LV.
.B lvcreate \-\-type cache\-pool \-L CacheSize \-n CachePoolLV VG FastPVs
.SH SEE ALSO
.BR lvm.conf (5),