Tiering and Unified Namespace¶
The DAOS tier can be tightly integrated with the Lustre parallel filesystem in which DAOS containers will be represented through the Lustre namespace. This capability is under development and is scheduled for DAOS v1.2.
Current state of work can be summarized as follow :
DAOS integration with Lustre uses the Lustre foreign file/dir feature (from LU-11376 and associated patches)
each time a DAOS POSIX container is created, using
daosutility and its '--path' UNS option, a Lustre foreign file/dir of 'daos' type is being created with a specific LOV/LMV EA content that will allow to store the DAOS pool and containers UUIDs.
Lustre Client patch for LU-12682, adds DAOS specific support to the Lustre foreign file/dir feature. It allows for foreign file/dir of
daostype to be presented and act as
<absolute-prefix>/<pool-uuid>/<container-uuid>a symlink to the Linux Kernel/VFS.
can be specified as the new
daos=<absolute-prefix>Lustre Client mount option, or also thru the new
llite.*.daos_prefixLustre dynamic tuneable. And both
and are extracted from foreign file/dir LOV/LMV EA.
to allow for symlink resolution and transparent access to DAOS concerned container content, it is expected that a DFuse/DFS instance/mount, of DAOS Server root, exists on
presenting all served pools/containers as
daosforeign support is enabled at mount time with
daos=option present, or dynamically thru
Migration to/from a POSIX filesystem¶
A dataset mover tool is under consideration to move a snapshot of a POSIX, MPI-IO or HDF5 container to a POSIX filesystem and vice versa. The copy will be performed at the POSIX or HDF5 level. The resulting HDF5 file over the POSIX filesystem will be accessible through the native HDF5 connector with the POSIX VFD.
The first version of the mover tool is currently scheduled for DAOS v1.4.
The mover tool will also eventually support the ability to serialize and deserialize a DAOS container to a set of POSIX files that can be stored or "parked" in an external POSIX filesystem. This transformation is agnostic to the data model and container type and will retain all DAOS internal metadata.