Local Pool Module

The localpool module can automatically create RADOS pools that are localized to a subset of the overall cluster. For example, by default, it will create a pool for each distinct rack in the cluster. This can be useful for some deployments that want to distribute some data locally as well as globally across the cluster .

Enabling

The localpool module is enabled with:

  1. ceph mgr module enable localpool

Configuring

The localpool module understands the following options:

  • subtree (default: rack): which CRUSH subtree type the module should create a pool for.

  • failure_domain (default: host): what failure domain we should separate data replicas across.

  • pg_num (default: 128): number of PGs to create for each pool

  • num_rep (default: 3): number of replicas for each pool. (Currently, pools are always replicated.)

  • min_size (default: none): value to set min_size to (unchanged from Ceph’s default if this option is not set)

  • prefix (default: by-$subtreetype-): prefix for the pool name.

These options are set via the config-key interface. For example, to change the replication level to 2x with only 64 PGs,

  1. ceph config set mgr mgr/localpool/num_rep 2
  2. ceph config set mgr mgr/localpool/pg_num 64