lvmvdo(7) — Linux manual page


LVMVDO(7)                                                      LVMVDO(7)

NAME         top

       lvmvdo — EXPERIMENTAL LVM Virtual Data Optimizer support

DESCRIPTION         top

       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.

VDO Terms         top

              VDO data LV
              large hidden LV with suffix _vdata created in a VG.
              used by VDO target to store all data and metadata blocks.

              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

              VDO LV
              created from VDOPoolLV
              appears blank after creation

VDO Usage         top

       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

       # 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

       # 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.

       # cat <<EOF > vdo.profile
       allocation {

       # 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

       # 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

       # 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

       # 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

       lvextend -L+AddingSize VG/VDOLV
       lvreduce -L-ReducingSize VG/VDOLV

       # 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.

       # lvchange -ay vg/vpool0_vdata
       # lvchange -an vg/vpool0_vdata

VDO Topics         top

   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.

       # 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.

       # 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.

       # 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

SEE ALSO         top

       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)

COLOPHON         top

       This page is part of the lvm2 (Logical Volume Manager 2) project.
       Information about the project can be found at 
       ⟨⟩.  If you have a bug report for
       this manual page, see ⟨⟩.
       This page was obtained from the tarball fetched
       from ⟨⟩ on 2020-12-18.
       If you discover any rendering problems in this HTML version of
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       original manual page), send a mail to

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)