lvmvdo(7) — Linux manual page

NAME | DESCRIPTION | VDO Terms | VDO Usage | VDO Topics | SEE ALSO | COLOPHON

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

       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

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

       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

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.

       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

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 
       ⟨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 2020-08-13.  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)