DMAPI restrictions for GPFS

All DMAPI APIs must be called from nodes that are in the cluster where the file system is created. DMAPI APIs may not be invoked from a remote cluster.

Furthermore, GPFS also places the following DMAPI API restrictions:
  • Running dm_get_events with the DM_EV_WAIT flag set causes the calling process to wait uninterruptibly.
  • Interacting with a handle after calling dm_handle_free will result in undefined behavior.
In addition to the DMAPI API restrictions, GPFS places the following restrictions on the use of file system snapshots when you have DMAPI enabled:
  • Snapshots cannot coexist with file systems using GPFS 3.1 or earlier.
  • GPFS 3.2 and later permits snapshots with DMAPI-enabled file systems. However, GPFS places the following restrictions on DMAPI access to the snapshot files:
    • The DM server may read files in a snapshot using dm_read_invis.
    • The DM server is not allowed to modify or delete the file using dm_write_invis or dm_punch_hole.
    • The DM server is not allowed to establish a managed region on the file.
    • Snapshot creation or deletion does not generate DMAPI namespace events.
    • Snapshots of a file are not managed regardless of the state of the original file and they do not inherit the DMAPI attributes of the original file.