6.8. Creating a RAID LV with DM integrity
When you create a RAID LV with device mapper (DM) integrity or add integrity to an existing RAID LV, it mitigates the risk of losing data due to soft corruption. Wait for the integrity synchronization and the RAID metadata to complete before using the LV. Otherwise, the background initialization might impact the LV’s performance.
Procédure
Create a RAID LV with DM integrity. The following example creates a new RAID LV with integrity named test-lv in the my_vg volume group, with a usable size of 256M and RAID level 1:
# lvcreate --type raid1 --raidintegrity y -L 256M -n test-lv my_vg Creating integrity metadata LV test-lv_rimage_0_imeta with size 8.00 MiB. Logical volume "test-lv_rimage_0_imeta" created. Creating integrity metadata LV test-lv_rimage_1_imeta with size 8.00 MiB. Logical volume "test-lv_rimage_1_imeta" created. Logical volume "test-lv" created.
NoteTo add DM integrity to an existing RAID LV, use the following command:
# lvconvert --raidintegrity y my_vg/test-lvAdding integrity to a RAID LV limits the number of operations that you can perform on that RAID LV.
Optional: Remove the integrity before performing certain operations.
# lvconvert --raidintegrity n my_vg/test-lv Logical volume my_vg/test-lv has removed integrity.
Vérification
View information about the added DM integrity:
View information about the test-lv RAID LV that was created in the my_vg volume group:
# lvs -a my_vg LV VG Attr LSize Origin Cpy%Sync test-lv my_vg rwi-a-r--- 256.00m 2.10 [test-lv_rimage_0] my_vg gwi-aor--- 256.00m [test-lv_rimage_0_iorig] 93.75 [test-lv_rimage_0_imeta] my_vg ewi-ao---- 8.00m [test-lv_rimage_0_iorig] my_vg -wi-ao---- 256.00m [test-lv_rimage_1] my_vg gwi-aor--- 256.00m [test-lv_rimage_1_iorig] 85.94 [...]The following describes different options from this output:
gattribute-
It is the list of attributes under the Attr column indicates that the RAID image is using integrity. The integrity stores the checksums in the
_imetaRAID LV. Cpy%Synccolumn- It indicates the synchronization progress for both the top level RAID LV and for each RAID image.
- RAID image
-
It is is indicated in the LV column by
raid_image_N. LVcolumn- It ensures that the synchronization progress displays 100% for the top level RAID LV and for each RAID image.
Display the type for each RAID LV:
# lvs -a my-vg -o+segtype LV VG Attr LSize Origin Cpy%Sync Type test-lv my_vg rwi-a-r--- 256.00m 87.96 raid1 [test-lv_rimage_0] my_vg gwi-aor--- 256.00m [test-lv_rimage_0_iorig] 100.00 integrity [test-lv_rimage_0_imeta] my_vg ewi-ao---- 8.00m linear [test-lv_rimage_0_iorig] my_vg -wi-ao---- 256.00m linear [test-lv_rimage_1] my_vg gwi-aor--- 256.00m [test-lv_rimage_1_iorig] 100.00 integrity [...]There is an incremental counter that counts the number of mismatches detected on each RAID image. View the data mismatches detected by integrity from
rimage_0under my_vg/test-lv:# lvs -o+integritymismatches my_vg/test-lv_rimage_0 LV VG Attr LSize Origin Cpy%Sync IntegMismatches [test-lv_rimage_0] my_vg gwi-aor--- 256.00m [test-lv_rimage_0_iorig] 100.00 0In this example, the integrity has not detected any data mismatches and thus the
IntegMismatchescounter shows zero (0).View the data integrity information in the
/var/log/messageslog files, as shown in the following examples:Exemple 6.1. Example of dm-integrity mismatches from the kernel message logs
device-mapper: integrity: dm-12: Checksum failed at sector 0x24e7
Exemple 6.2. Example of dm-integrity data corrections from the kernel message logs
md/raid1:mdX: read error corrected (8 sectors at 9448 on dm-16)
Ressources supplémentaires
-
lvcreate(8)andlvmraid(7)man pages
