Speaker
Mr
Martin Radicke
(DESY Hamburg)
Description
The dCache software has become a major storage element in the WLCG, providing
high-speed file transfers by caching datasets on potentially thousands of disk
servers in front of tertiary storage. Currently dCache's model of separately
connecting all disk servers to the tape backend leads to locally controlled flush and
restore behavior has shown some inefficiencies in respect of tape drive utilization.
This paper reports on enhancements to dCache and its interface to Hierarchical
Storage Management Systems through a new module to centrally control the tape
backend. The focus is to optimize the mount behavior, parallelization of requests
and utilization of the available tape drive data rate. dCache is widely deployed in
production instances, so improvements will be phased to maintain backwards
compatibility. The first phase has been achieved by introducing the Flushmanager, a
module to collect and coordinate all tape write operations. The second phase of
implementation will be about collecting metadata and restore requests respectively.
This information will be provided to user-added plug-ins via a clean interface, for
managing restore requests using customized strategies. The third phase will focus on
resource knowledge and drive steering with a generic and feature-rich interface to
unify access to common Tertiary Storage Systems. The final phase will be the
aggregation of the existing Flush- and Restore-Manager to implement a single module
for controlling tape backends through dCache, offering a extensible programming
framework to the community.
Primary author
Mr
Martin Radicke
(DESY Hamburg)
Co-author
Dr
Patrick Fuhrmann
(DESY Hamburg)