mirror of
git://sourceware.org/git/lvm2.git
synced 2025-01-03 05:18:29 +03:00
man: lvmthin pool space exhaustion
Initial description and instructions for data/metadata space exhaustion.
This commit is contained in:
David Teigland
parent
7b11b1b4b5
commit
f242c0611d
102
man/lvmthin.7.in
102
man/lvmthin.7.in
@ -17,18 +17,18 @@ blocks in a thin LV are allocated (during use) from a special "thin pool
|
||||
LV". The thin pool LV contains blocks of physical storage, and blocks in
|
||||
thin LVs just reference blocks in the thin pool LV.
|
||||
|
||||
A thin pool LV must be created before thin LV's can be created within it.
|
||||
A thin pool LV is created by combining two standard LV's: a large data LV
|
||||
A thin pool LV must be created before thin LVs can be created within it.
|
||||
A thin pool LV is created by combining two standard LVs: a large data LV
|
||||
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.
|
||||
|
||||
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 LV's
|
||||
thin LV and its snapshot are shared. Snapshots may be taken of thin LVs
|
||||
or of other thin snapshots. Blocks common to recursive snapshots are also
|
||||
shared in the thin pool. There is no limit to or degradation from
|
||||
sequences of snapshots.
|
||||
|
||||
As thin LV's or snapshot LV's 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
|
||||
may need to be supplied. This is done by extending the thin pool data LV
|
||||
with additional physical space from the VG. Removing thin LVs or
|
||||
@ -146,7 +146,7 @@ The primary method for using lvm thin provisioning:
|
||||
|
||||
Create a new thin LV from the thin pool LV.
|
||||
The thin LV is created with a virtual size.
|
||||
Multiple new thin LV's may be created in the thin pool.
|
||||
Multiple new thin LVs may be created in the thin pool.
|
||||
Thin LV names must be unique in the VG.
|
||||
The thinpool argument specifies which thin pool will
|
||||
contain the ThinLV.
|
||||
@ -221,7 +221,7 @@ Automatic pool metadata LV
|
||||
.br
|
||||
Activation of thin snapshots
|
||||
.br
|
||||
Removing thin pool LV's, thin LV's and snapshots
|
||||
Removing thin pool LVs, thin LVs and snapshots
|
||||
.br
|
||||
Manually manage free data space of thin pool LV
|
||||
.br
|
||||
@ -231,6 +231,10 @@ Using fstrim to increase free space in a thin pool LV
|
||||
.br
|
||||
Automatically extend thin pool LV
|
||||
.br
|
||||
Data space exhaustion
|
||||
.br
|
||||
Metadata space exhaustion
|
||||
.br
|
||||
Zeroing
|
||||
.br
|
||||
Discard
|
||||
@ -348,7 +352,7 @@ If the thin_check command finds a problem with the metadata,
|
||||
the thin pool LV is not activated, and the thin pool metadata should
|
||||
be repaired.
|
||||
|
||||
Command to repair a thin pool LV:
|
||||
Command to repair a thin pool:
|
||||
.nf
|
||||
lvconvert --repair VG/ThinPoolLV
|
||||
.fi
|
||||
@ -460,7 +464,7 @@ See lvm.conf auto_set_activation_skip to set default usage of
|
||||
activation skip.
|
||||
|
||||
|
||||
.SS Removing thin pool LV's, thin LV's and snapshots
|
||||
.SS Removing thin pool LVs, thin LVs and snapshots
|
||||
|
||||
\&
|
||||
|
||||
@ -471,7 +475,7 @@ thin LVs and snapshots.
|
||||
Removing a thin pool LV removes both the data LV and metadata LV
|
||||
and returns the space to the VG.
|
||||
|
||||
lvremove of thin pool LV's, thin LV's and snapshots cannot be
|
||||
lvremove of thin pool LVs, thin LVs and snapshots cannot be
|
||||
reversed with vgcfgrestore.
|
||||
|
||||
vgcfgbackup does not back up thin pool metadata.
|
||||
@ -486,6 +490,9 @@ with the lvs command. Free space can be added by extending
|
||||
the thin pool LV.
|
||||
|
||||
.nf
|
||||
Command to extend thin pool data space:
|
||||
lvextend -L Size VG/ThinPoolLV
|
||||
|
||||
Example
|
||||
|
||||
1. A thin pool LV is using 26.96% of its data blocks.
|
||||
@ -514,6 +521,11 @@ fstrim on the file system using a thin LV.
|
||||
The available metadata space in a thin pool LV can be displayed
|
||||
with the lvs -o+metadata_percent command.
|
||||
|
||||
Command to extend thin pool metadata space:
|
||||
.nf
|
||||
lvextend -L Size VG/ThinPoolLV_tmeta
|
||||
.fi
|
||||
|
||||
Example
|
||||
|
||||
1. A thin pool LV is using 12.40% of its metadata blocks.
|
||||
@ -639,6 +651,78 @@ For a 1G pool, using 700M will trigger a resize to 1.2G. When the usage exceeds
|
||||
840M, the pool will be extended to 1.44G, and so on.
|
||||
|
||||
|
||||
.SS Data space exhaustion
|
||||
|
||||
\&
|
||||
|
||||
If thin pool data space is exhausted, writes to thin LVs will be queued
|
||||
until the the data space is extended. Reading is still possible.
|
||||
|
||||
When data space is exhausted, the lvs command displays 100 under Data% for
|
||||
the thin pool LV:
|
||||
|
||||
.nf
|
||||
# lvs vg/pool0
|
||||
LV VG Attr LSize Pool Origin Data%
|
||||
pool0 vg twi-a-tz-- 512.00m 100.00
|
||||
.fi
|
||||
|
||||
A thin pool can run out of data blocks for any of the following reasons:
|
||||
|
||||
1. Automatic extension of the thin pool is disabled, and the thin pool is
|
||||
not manually extended. (Disabling automatic extension is not
|
||||
recommended.)
|
||||
|
||||
2. The dmeventd daemon is not running and the thin pool is not manually
|
||||
extended. (Disabling dmeventd is not recommended.)
|
||||
|
||||
3. Automatic extension of the thin pool is too slow given the rate of
|
||||
writes to thin LVs in the pool. (This can be addressed by tuning the
|
||||
thin_pool_autoextend_threshold and thin_pool_autoextend_percent.)
|
||||
|
||||
4. The VG does have enough free blocks to extend the thin pool.
|
||||
|
||||
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
|
||||
LV".
|
||||
|
||||
|
||||
.SS Metadata space exhaustion
|
||||
|
||||
\&
|
||||
|
||||
If thin pool metadata space is exhausted (or a thin pool metadata
|
||||
operation fails), errors will be returned for IO operations on thin LVs.
|
||||
|
||||
When metadata space is exhausted, the lvs command displays 100 under Meta%
|
||||
for the thin pool LV:
|
||||
|
||||
.nf
|
||||
# lvs -o lv_name,size,data_percent,metadata_percent vg/pool0
|
||||
LV LSize Data% Meta%
|
||||
pool0 100.00
|
||||
.fi
|
||||
|
||||
The same reasons for thin pool data space exhaustion apply to thin pool
|
||||
metadata space.
|
||||
|
||||
Metadata space exhaustion can lead to inconsistent thin pool metadata and
|
||||
inconsistent file systems, so the response requires offline checking and
|
||||
repair.
|
||||
|
||||
1. Deactivate the thin pool LV, or reboot the system if this is not possible.
|
||||
|
||||
2. Repair thin pool with lvconvert --repair.
|
||||
.br
|
||||
See "Metadata check and repair".
|
||||
|
||||
3. Extend pool metadata space with lvextend VG/ThinPoolLV_tmeta.
|
||||
.br
|
||||
See "Manually manage free metadata space of a thin pool LV".
|
||||
|
||||
4. Check and repair file system with fsck.
|
||||
|
||||
|
||||
.SS Zeroing
|
||||
|
||||
\&
|
||||
|
||||
Loading…
Reference in New Issue
Block a user