Observing the data migration

When you add or remove an OSD to the CRUSH map, Ceph begins rebalancing the data by migrating placement groups to the new or existing OSD(s).

You can observe the data migration by using the ceph-w command.

Prerequisites

  • A running IBM Storage Ceph cluster.

  • Recently added or removed an OSD.

Procedure

  1. To observe the data migration:

    Example 

    [ceph: root@host01 /]# ceph -w

  2. Watch as the placement group states change from active+clean to active, some degraded objects, and finally active+clean when migration completes.

  3. To exit the utility, press Ctrl + C.