Ceph volume lvm plugin

By making use of LVM tags, the lvm sub-command is able to store and re-discover by querying devices associated with OSDs so they can be activated. This includes support for lvm-based technologies like dm-cache as well.

When using ceph-volume, the use of dm-cache is transparent, and treats dm-cache like a logical volume. The performance gains and losses when using dm-cache will depend on the specific workload. Generally, random and sequential reads will see an increase in performance at smaller block sizes. While random and sequential writes will see a decrease in performance at larger block sizes.

To use the LVM plugin, add lvm as a subcommand to the ceph-volume command within the cephadm shell:

[ceph: root@host01 /]# ceph-volume lvm

Following are the lvm subcommands:

  • prepare - Format an LVM device and associate it with an OSD.

  • activate - Discover and mount the LVM device associated with an OSD ID and start the Ceph OSD.

  • list - List logical volumes and devices associated with Ceph.

  • batch - Automatically size devices for multi-OSD provisioning with minimal interaction.

  • deactivate - Deactivate OSDs.

  • create - Create a new OSD from an LVM device.

  • trigger - A systemd helper to activate an OSD.

  • zap - Removes all data and filesystems from a logical volume or partition.

  • migrate - Migrate BlueFS data from to another LVM device.

  • new-wal - Allocate new WAL volume for the OSD at specified logical volume.

  • new-db - Allocate new DB volume for the OSD at specified logical volume.

Note: Using the create subcommand combines the prepare and activate subcommands into one subcommand.