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man: more lvmthin discard references

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and some fixes from Tom.
This commit is contained in:
David Teigland 2014-05-14 09:44:09 -05:00
parent 3b989e317f
commit 044b796800
1 changed files with 13 additions and 8 deletions
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man/lvmthin.7.in
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@ -23,10 +23,10 @@ that will hold blocks for thin LVs, and a metadata LV that will hold
metadata. The metadata tracks which data blocks belong to each thin LV. metadata. The metadata tracks which data blocks belong to each thin LV.
Snapshots of thin LVs are efficient because the data blocks common to a Snapshots of thin LVs are efficient because the data blocks common to a
thin LV and its snapshot are shared. Snapshots may be taken of thin LVs thin LV and any of its snapshots are shared. Snapshots may be taken of
or of other thin snapshots. Blocks common to recursive snapshots are also thin LVs or of other thin snapshots. Blocks common to recursive snapshots
shared in the thin pool. There is no limit to or degradation from are also shared in the thin pool. There is no limit to or degradation
sequences of snapshots. from sequences of snapshots.
As thin LVs or snapshot LVs are written to, they consume data blocks in As thin LVs or snapshot LVs are written to, they consume data blocks in
the thin pool. As free data blocks in the pool decrease, more free blocks the thin pool. As free data blocks in the pool decrease, more free blocks
@ -620,6 +620,9 @@ pool0 vg twi-a-tz-- 10.00g 47.01 21.03
thin1 vg Vwi-aotz-- 100.00g pool0 2.70 thin1 vg Vwi-aotz-- 100.00g pool0 2.70
.fi .fi
The "Discard" section covers an option for automatically freeing data
space in a thin pool.
.SS Automatically extend thin pool LV .SS Automatically extend thin pool LV
@ -691,7 +694,7 @@ extended. (Disabling dmeventd is not recommended.)
writes to thin LVs in the pool. (This can be addressed by tuning the writes to thin LVs in the pool. (This can be addressed by tuning the
thin_pool_autoextend_threshold and thin_pool_autoextend_percent.) thin_pool_autoextend_threshold and thin_pool_autoextend_percent.)
4. The VG does have enough free blocks to extend the thin pool. 4. The VG does not have enough free blocks to extend the thin pool.
The response to data space exhaustion is to extend the thin pool. This is The response to data space exhaustion is to extend the thin pool. This is
described in the section "Manually manage free data space of thin pool described in the section "Manually manage free data space of thin pool
@ -768,8 +771,10 @@ controls the default zeroing mode used when creating a thin pool.
\& \&
The discard behavior of a thin pool LV determines how discard requests The discard behavior of a thin pool LV determines how discard requests are
are handled. Possible discard behaviors: handled. Enabling discard under a file system may adversely affect the
file system performance (see the section on fstrim for an alternative.)
Possible discard behaviors:
ignore: Ignore any discards that are received. ignore: Ignore any discards that are received.
@ -933,7 +938,7 @@ and combines the two into a thin pool LV.
lvcreate -L LargeSize --thinpool VG/ThinPoolLV lvcreate -L LargeSize --thinpool VG/ThinPoolLV
Example Example
# lvcreate -l1 --thinpool vg/pool0 # lvcreate -L8M --thinpool vg/pool0
# lvs vg/pool0 # lvs vg/pool0
LV VG Attr LSize Pool Origin Data% LV VG Attr LSize Pool Origin Data%