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dm-integrity stores checksums of the data written to an LV, and returns an error if data read from the LV does not match the previously saved checksum. When used on raid images, dm-raid will correct the error by reading the block from another image, and the device user sees no error. The integrity metadata (checksums) are stored on an internal LV allocated by lvm for each linear image. The internal LV is allocated on the same PV as the image. Create a linear LV with integrity: lvcreate --integrity y [options] Create a raid LV with an integrity layer over each raid image (for raid levels 1,4,5,6,10): lvcreate --type raidN --integrity y [options] Add an integrity layer to an existing linear LV, or to each image of an existing raid LV: lvconvert --integrity y LV Remove the integrity layer from a linear LV, or from the images of a raid LV: lvconvert --integrity n LV Settings The kernel module has numerous tunable settings that can be specified using: --integritysettings String where the String includes one or more key/value pairs, e.g. --integritysettings "mode=J" The most relevant setting is the mode which controls how dm-integrity keeps data consisent in case of a crash. To use a journal, set mode=J, to use a bitmap set mode=B. (default B). Initialization When a new LV with integrity is created, or integrity is added to an LV, the kernel needs to initialize the integrity metadata/checksums for all blocks in the LV. The data corruption checking performed by dm-integrity will only operate on areas of the LV that are already initialized. The progress of integrity initialization is reported by the "syncpercent" LV reporting field (and under the Cpy%Sync lvs column.) $ lvconvert --integrity y vg/lv $ lvs vg/lv LV VG Attr LSize Origin Cpy%Sync lv vg gwi-a----- 1.00g [lv_iorig] 85.16 Examples create a linear LV with integrity: $ lvcreate --integrity y -n lvex -L1G vg $ lvs -a foo LV VG Attr LSize Origin Cpy%Sync lvex vg gwi-a----- 1.00g [lvex_iorig] 21.48 [lvex_imeta] vg ewi-ao---- 12.00m [lvex_iorig] vg -wi-ao---- 1.00g create a linear LV, then add integrity: $ lvcreate -n lvex -L1G foo Logical volume "lvex" created. $ lvs -a foo LV VG Attr LSize lvex foo -wi-a----- 1.00g $ lvconvert --integrity y foo/lvex Creating integrity metadata LV lvex_imeta with size 12.00 MiB. Logical volume "lvex_imeta" created. Logical volume foo/lvex has added integrity. $ lvs -a foo LV VG Attr LSize Origin Cpy%Sync lvex foo gwi-a----- 1.00g [lvex_iorig] 17.19 [lvex_imeta] foo ewi-ao---- 12.00m [lvex_iorig] foo -wi-ao---- 1.00g create a raid1 LV with integrity: $ lvcreate --type raid1 -m1 --integrity y -n rr -L1G foo Creating integrity metadata LV rr_rimage_0_imeta with size 12.00 MiB. Logical volume "rr_rimage_0_imeta" created. Creating integrity metadata LV rr_rimage_1_imeta with size 12.00 MiB. Logical volume "rr_rimage_1_imeta" created. Logical volume "rr" created. $ lvs -a foo LV VG Attr LSize Origin Cpy%Sync rr foo rwi-a-r--- 1.00g 4.93 [rr_rimage_0] foo gwi-aor--- 1.00g [rr_rimage_0_iorig] 41.02 [rr_rimage_0_imeta] foo ewi-ao---- 12.00m [rr_rimage_0_iorig] foo -wi-ao---- 1.00g [rr_rimage_1] foo gwi-aor--- 1.00g [rr_rimage_1_iorig] 39.45 [rr_rimage_1_imeta] foo ewi-ao---- 12.00m [rr_rimage_1_iorig] foo -wi-ao---- 1.00g [rr_rmeta_0] foo ewi-aor--- 4.00m [rr_rmeta_1] foo ewi-aor--- 4.00m create a raid1 LV, then add integrity: $ lvcreate --type raid1 -m1 -n rr -L1G foo Creating integrity metadata LV rr_rimage_0_imeta with size 12.00 MiB. Logical volume "rr_rimage_0_imeta" created. Creating integrity metadata LV rr_rimage_1_imeta with size 12.00 MiB. Logical volume "rr_rimage_1_imeta" created. Logical volume "rr" created. $ lvs -a foo LV VG Attr LSize Origin Cpy%Sync rr foo rwi-aor--- 1.00g 0.00 [rr_rimage_0] foo gwi-aor--- 1.00g [rr_rimage_0_iorig] 17.58 [rr_rimage_0_imeta] foo ewi-ao---- 12.00m [rr_rimage_0_iorig] foo -wi-ao---- 1.00g [rr_rimage_1] foo gwi-aor--- 1.00g [rr_rimage_1_iorig] 15.62 [rr_rimage_1_imeta] foo ewi-ao---- 12.00m [rr_rimage_1_iorig] foo -wi-ao---- 1.00g [rr_rmeta_0] foo ewi-aor--- 4.00m [rr_rmeta_1] foo ewi-aor--- 4.00m $ lvconvert --integrity y foo/rr Logical volume foo/rr has added integrity. $ lvs -a foo LV VG Attr LSize Origin Cpy%Sync rr foo rwi-a-r--- 1.00g 9.18 [rr_rimage_0] foo gwi-aor--- 1.00g [rr_rimage_0_iorig] 65.62 [rr_rimage_0_imeta] foo ewi-ao---- 12.00m [rr_rimage_0_iorig] foo -wi-ao---- 1.00g [rr_rimage_1] foo gwi-aor--- 1.00g [rr_rimage_1_iorig] 64.84 [rr_rimage_1_imeta] foo ewi-ao---- 12.00m [rr_rimage_1_iorig] foo -wi-ao---- 1.00g [rr_rmeta_0] foo ewi-aor--- 4.00m [rr_rmeta_1] foo ewi-aor--- 4.00m