.TH "LVMVDO" "7" "LVM TOOLS #VERSION#" "Red Hat, Inc" "\"" .SH NAME lvmvdo \(em EXPERIMENTAL LVM Virtual Data Optimizer support .SH DESCRIPTION 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 \fBlvm\fP(8) standard VDO userspace tools \fBvdoformat\fP(8) and currently non-standard kernel VDO module "\fIkvdo\fP" needs to be installed on the system. The "\fIkvdo\fP" module implements fine-grained storage virtualization, thin provisioning, block sharing, and compression; the "\fIuds\fP" module provides memory-efficient duplicate identification. The userspace tools include \fBvdostats\fP(8) for extracting statistics from those volumes. .SH VDO Terms .TP VDODataLV .br VDO data LV .br large hidden LV with suffix _vdata created in a VG. .br used by VDO target to store all data and metadata blocks. .TP VDOPoolLV .br VDO pool LV .br maintains virtual for LV(s) stored in attached VDO data LV and it has same size. .br contains VDOLV(s) (currently supports only a single VDOLV). .TP VDOLV .br VDO LV .br created from VDOPoolLV .br appears blank after creation .SH VDO Usage The primary methods for using VDO with lvm2: .SS 1. Create VDOPoolLV with VDOLV Create an VDOPoolLV that will holds VDO data togehther 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. .nf .B lvcreate --type vdo -n VDOLV -L DataSize -V LargeVirtualSize VG/VDOPoolLV .B lvcreate --vdo -L DataSize VG .fi .I Example .br .nf # lvcreate --type vdo -n vdo0 -L 10G -V 100G vg/vdopool0 # mkfs.ext4 -E nodiscard /dev/vg/vdo0 .fi .SS 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 \fBIRREVERSIBLY DESTROYING\fP content of such volume, as it's being immediatelly formated by \fBvdoformat\fP(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. .nf .B lvconvert --type vdo-pool -n VDOLV -V VirtualSize VG/VDOPoolLV .B lvconvert --vdopool VG/VDOPoolLV .fi .I Example .br .nf # lvconvert --type vdo-pool -n vdo0 -V10G vg/existinglv .fi .SS 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 \fBlvmconfig --type full\fP for detailed description of all individual vdo settings. .I Example .br .nf # cat < 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 .fi .SS 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). .nf .B lvchange --compression [y|n] --deduplication [y|n] VG/VDOPoolLV .fi .I Example .br .nf # lvchange --compression n vg/vdpool0 # lvchange --deduplication y vg/vdpool1 .fi .SS 4. Checking usage of VDOPoolLV To quickly check how much data of VDOPoolLV are already consumed use \fBlvs\fP(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 \fBvdostats\fP(8) command. Note: \fBvdostats\fP(8) currently understands only /dev/mapper device names. .I Example .br .nf # 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 ... .fi .SS 4. Extending VDOPoolLV size Adding more space to hold VDO data and metadata can be made via extension of VDODataLV with commands \fBlvresize\fP(8), \fBlvextend\fP(8). Note: Size of VDOPoolLV cannot be reduced. .nf .B lvextend -L+AddingSize VG/VDOPoolLV .fi .I Example .br .nf # lvextend -L+50G vg/vdopool0 # lvresize -L300G vg/vdopool1 .fi .SS 4. Extending or reducing VDOLV size VDO LV can be extended or reduced as standard LV with commands \fBlvresize\fP(8), \fBlvextend\fP(8), \fBlvreduce\fP(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. .nf .B lvextend -L+AddingSize VG/VDOLV .B lvreduce -L-ReducingSize VG/VDOLV .fi .I Example .br .nf # lvextend -L+50G vg/vdo0 # lvreduce -L-50G vg/vdo1 # lvresize -L200G vg/vdo2 .fi .SS 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. .I Example .br .nf # lvchange -ay vg/vpool0_vdata # lvchange -an vg/vpool0_vdata .fi .SH VDO Topics .SS 1. Stacking VDO User can convert/stack VDO with existing volumes. .SS 2. VDO on top of raid Using Raid type LV for VDO Data LV. .I Example .br .nf # lvcreate --type raid1 -L 5G -n vpool vg # lvconvert --type vdo-pool -V 10G vg/vpool .fi .SS 3. Caching VDODataLV, VDOPoolLV Cache VDO Data LV (accepts also VDOPoolLV. .I Example .br .nf # 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 .fi .SS 3. Caching VDOLV Cache VDO LV. .I Example .br .nf # 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 .fi .br \& .SH SEE ALSO .BR lvm (8), .BR lvm.conf (5), .BR lvmconfig (8), .BR lvcreate (8), .BR lvconvert (8), .BR lvchange (8), .BR lvextend (8), .BR lvreduce (8), .BR lvresize (8), .BR lvremove (8), .BR lvs (8), .BR vdo (8), .BR vdoformat (8), .BR vdostats (8), .BR mkfs (8)