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NAME | DESCRIPTION | VDO Terms | VDO Usage | VDO Topics | SEE ALSO | COLOPHON |
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LVMVDO(7) LVMVDO(7)
lvmvdo — EXPERIMENTAL LVM Virtual Data Optimizer support
VDO (which includes kvdo and vdo) is software that provides
inline block-level deduplication, compression, and thin
provisioning capabilities for primary storage.
Deduplication is a technique for reducing the consumption of
storage resources by eliminating multiple copies of duplicate
blocks. Compression takes the individual unique blocks and
shrinks them with coding algorithms; these reduced blocks are
then efficiently packed together into physical blocks. Thin
provisioning manages the mapping from LBAs presented by VDO to
where the data has actually been stored, and also eliminates any
blocks of all zeroes.
With deduplication, instead of writing the same data more than
once each duplicate block is detected and recorded as a reference
to the original block. VDO maintains a mapping from logical block
addresses (used by the storage layer above VDO) to physical block
addresses (used by the storage layer under VDO). After
deduplication, multiple logical block addresses may be mapped to
the same physical block address; these are called shared blocks
and are reference-counted by the software.
With VDO's compression, multiple blocks (or shared blocks) are
compressed with the fast LZ4 algorithm, and binned together where
possible so that multiple compressed blocks fit within a 4 KB
block on the underlying storage. Mapping from LBA is to a
physical block address and index within it for the desired
compressed data. All compressed blocks are individually reference
counted for correctness.
Block sharing and block compression are invisible to applications
using the storage, which read and write blocks as they would if
VDO were not present. When a shared block is overwritten, a new
physical block is allocated for storing the new block data to
ensure that other logical block addresses that are mapped to the
shared physical block are not modified.
For usage of VDO with lvm(8) standard VDO userspace tools
vdoformat(8) and currently non-standard kernel VDO module "kvdo"
needs to be installed on the system.
The "kvdo" module implements fine-grained storage virtualization,
thin provisioning, block sharing, and compression; the "uds"
module provides memory-efficient duplicate identification. The
userspace tools include vdostats(8) for extracting statistics
from those volumes.
VDODataLV
VDO data LV
large hidden LV with suffix _vdata created in a VG.
used by VDO target to store all data and metadata blocks.
VDOPoolLV
VDO pool LV
maintains virtual for LV(s) stored in attached VDO data LV
and it has same size.
contains VDOLV(s) (currently supports only a single
VDOLV).
VDOLV
VDO LV
created from VDOPoolLV
appears blank after creation
The primary methods for using VDO with lvm2:
1. Create VDOPoolLV with VDOLV
Create an VDOPoolLV that will holds VDO data together with
virtual size VDOLV, that user can use. When the virtual size is
not specified, then such LV is created with maximum size that
always fits into data volume even if there cannot happen any
deduplication and compression (i.e. it can hold uncompressible
content of /dev/urandom). When the name of VDOPoolLV is not
specified, it tales name from sequence of vpool0, vpool1 ...
Note: As the performance of TRIM/Discard operation is slow for
large volumes of VDO type, please try to avoid sending discard
requests unless necessary as it may take considerable amount of
time to finish discard operation.
lvcreate --type vdo -n VDOLV -L DataSize -V LargeVirtualSize VG/VDOPoolLV
lvcreate --vdo -L DataSize VG
Example
# lvcreate --type vdo -n vdo0 -L 10G -V 100G vg/vdopool0
# mkfs.ext4 -E nodiscard /dev/vg/vdo0
2. Create VDOPoolLV and convert existing LV into VDODataLV
Convert an already created/existing LV into a volume that can
hold VDO data and metadata (a volume reference by VDOPoolLV).
User will be prompted to confirm such conversion as it is
IRREVERSIBLY DESTROYING content of such volume, as it's being
immediately formatted by vdoformat(8) as VDO pool data volume.
User can specify virtual size of associated VDOLV with this
VDOPoolLV. When the virtual size is not specified, it will set
to the maximum size that can keep 100% uncompressible data there.
lvconvert --type vdo-pool -n VDOLV -V VirtualSize VG/VDOPoolLV
lvconvert --vdopool VG/VDOPoolLV
Example
# lvconvert --type vdo-pool -n vdo0 -V10G vg/existinglv
3. Change default setting used for creating VDOPoolLV
VDO allows to set large variety of option. Lots of these setting
can be specified by lvm.conf or profile settings. User can
prepare number of different profiles and just specify profile
file name. Check output of lvmconfig --type full for detailed
description of all individual vdo settings.
Example
# cat <<EOF > vdo.profile
allocation {
vdo_use_compression=1
vdo_use_deduplication=1
vdo_use_metadata_hints=1
vdo_minimum_io_size=4096
vdo_block_map_cache_size_mb=128
vdo_block_map_period=16380
vdo_check_point_frequency=0
vdo_use_sparse_index=0
vdo_index_memory_size_mb=256
vdo_slab_size_mb=2048
vdo_ack_threads=1
vdo_bio_threads=1
vdo_bio_rotation=64
vdo_cpu_threads=2
vdo_hash_zone_threads=1
vdo_logical_threads=1
vdo_physical_threads=1
vdo_write_policy="auto"
vdo_max_discard=1
}
EOF
# lvcreate --vdo -L10G --metadataprofile vdo.profile vg/vdopool0
# lvcreate --vdo -L10G --config 'allocation/vdo_cpu_threads=4' vg/vdopool1
4. Change compression and deduplication of VDOPoolLV
Disable or enable compression and deduplication for VDO pool LV
(the volume that maintains all VDO LV(s) associated with it).
lvchange --compression [y|n] --deduplication [y|n] VG/VDOPoolLV
Example
# lvchange --compression n vg/vdpool0
# lvchange --deduplication y vg/vdpool1
4. Checking usage of VDOPoolLV
To quickly check how much data of VDOPoolLV are already consumed
use lvs(8). Field Data% will report how much data occupies
content of virtual data for VDOLV and how much space is already
consumed with all the data and metadata blocks in VDOPoolLV. For
a detailed description use vdostats(8) command.
Note: vdostats(8) currently understands only /dev/mapper device
names.
Example
# lvcreate --type vdo -L10G -V20G -n vdo0 vg/vdopool0
# mkfs.ext4 -E nodiscard /dev/vg/vdo0
# lvs -a vg
LV VG Attr LSize Pool Origin Data%
vdo0 vg vwi-a-v--- 20.00g vdopool0 0.01
vdopool0 vg dwi-ao---- 10.00g 30.16
[vdopool0_vdata] vg Dwi-ao---- 10.00g
# vdostats --all /dev/mapper/vg-vdopool0
/dev/mapper/vg-vdopool0 :
version : 30
release version : 133524
data blocks used : 79
...
4. Extending VDOPoolLV size
Adding more space to hold VDO data and metadata can be made via
extension of VDODataLV with commands lvresize(8), lvextend(8).
Note: Size of VDOPoolLV cannot be reduced.
lvextend -L+AddingSize VG/VDOPoolLV
Example
# lvextend -L+50G vg/vdopool0
# lvresize -L300G vg/vdopool1
4. Extending or reducing VDOLV size
VDO LV can be extended or reduced as standard LV with commands
lvresize(8), lvextend(8), lvreduce(8).
Note: Reduction needs to process TRIM for reduced disk area to
unmap used data blocks from VDOPoolLV and it may take a long
time.
lvextend -L+AddingSize VG/VDOLV
lvreduce -L-ReducingSize VG/VDOLV
Example
# lvextend -L+50G vg/vdo0
# lvreduce -L-50G vg/vdo1
# lvresize -L200G vg/vdo2
5. Component activation of VDODataLV
VDODataLV can be activated separately as component LV for
examination purposes. It activates data LV in read-only mode and
cannot be modified. If the VDODataLV is active as component, any
upper LV using this volume CANNOT be activated. User has to
deactivate VDODataLV first to continue to use VDOPoolLV.
Example
# lvchange -ay vg/vpool0_vdata
# lvchange -an vg/vpool0_vdata
1. Stacking VDO
User can convert/stack VDO with existing volumes.
2. VDO on top of raid
Using Raid type LV for VDO Data LV.
Example
# lvcreate --type raid1 -L 5G -n vpool vg
# lvconvert --type vdo-pool -V 10G vg/vpool
3. Caching VDODataLV, VDOPoolLV
Cache VDO Data LV (accepts also VDOPoolLV.
Example
# lvcreate -L 5G -V 10G -n vdo1 vg/vpool
# lvcreate --type cache-pool -L 1G -n cpool vg
# lvconvert --cache --cachepool vg/cpool vg/vpool
# lvconvert --uncache vg/vpool
3. Caching VDOLV
Cache VDO LV.
Example
# lvcreate -L 5G -V 10G -n vdo1 vg/vpool
# lvcreate --type cache-pool -L 1G -n cpool vg
# lvconvert --cache --cachepool vg/cpool vg/vdo1
# lvconvert --uncache vg/vdo1
lvm(8), lvm.conf(5), lvmconfig(8), lvcreate(8), lvconvert(8),
lvchange(8), lvextend(8), lvreduce(8), lvresize(8), lvremove(8),
lvs(8), vdo(8), vdoformat(8), vdostats(8), mkfs(8)
This page is part of the lvm2 (Logical Volume Manager 2) project.
Information about the project can be found at
⟨http://www.sourceware.org/lvm2/⟩. If you have a bug report for
this manual page, see ⟨https://github.com/lvmteam/lvm2/issues⟩.
This page was obtained from the tarball
https://github.com/lvmteam/lvm2/archive/v2_03_10.tar.gz fetched
from ⟨https://github.com/lvmteam/lvm2/releases⟩ on 2020-12-18.
If you discover any rendering problems in this HTML version of
the page, or you believe there is a better or more up-to-date
source for the page, or you have corrections or improvements to
the information in this COLOPHON (which is not part of the
original manual page), send a mail to man-pages@man7.org
Red Hat, Inc LVM TOOLS 2.03.10(2) (2020-08-09) LVMVDO(7)
Pages that refer to this page: lvchange(8), lvconvert(8), lvcreate(8), lvextend(8), lvresize(8)
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