- DPM Head Node: The machine hosting SRM daemons for DPM. For a typical DPM Yaim Install this machine also hosts the DPM (pool manager) and DPNS (name server) daemons and (MySQL) databases; but this is not strictly necessary - DPM can have these daemons hosted elsewhere (and even have the backend database server for these daemons on a different machine again). As of DPM 1.9.x, DPM can also operate using its future DOME mechanism, which obsoletes the DPM and DPNS daemons in favour of a lighter-weight infrastructure.
- DPM Disk Server: A machine hosting filesystems which form part of a DPM Pool.
- Filesystem: A single (usually POSIX) filesystem hosted on a DPM machine which forms part of a DPM Pool. The most important property which can be set on a filesystem is status, in particular filesystems can be marked RDONLY which will prevent any incoming files from being written to this filesystem, or DISABLED, which prevents any accesses at all.
- Pool: An aggregation of filesystems to form a logical entity inside DPM. Many properties can be set at the pool level: default SRM storage class (volatile, durable), default file size, filesystem selection algorithm, reservation for a particular VO. Files written to a pool are distributed (at the file level) across all filesystems in the pool, via a weighting mechanism (by default, equally for each filesystem).
root of se2-gla:~# dpm-qryconf POOL srmStore DEFSIZE 1024.00M GC_START_THRESH 0 GC_STOP_THRESH 0 DEFPINTIME 100000 PUT_RETENP 86400 FSS_POLICY maxfreespace GC_POLICY lru RS_POLICY fifo GID 0 S_TYPE - CAPACITY 2.63T FREE 2.32T ( 88.4%) pool1-gla.scotgrid.ac.uk /gridstorage/c1 CAPACITY 538.04G FREE 452.35G ( 84.1%) pool1-gla.scotgrid.ac.uk /gridstorage/d1 CAPACITY 538.04G FREE 454.27G ( 84.4%) RDONLY pool1-gla.scotgrid.ac.uk /gridstorage/e1 CAPACITY 538.04G FREE 455.26G ( 84.6%) RDONLY pool1-gla.scotgrid.ac.uk /gridstorage/f1 CAPACITY 538.04G FREE 453.32G ( 84.3%) RDONLY pool1-gla.scotgrid.ac.uk /gridstorage/g1 CAPACITY 538.04G FREE 451.75G ( 84.0%) pool2-gla.scotgrid.ac.uk /gridstorage/sdc1 CAPACITY 1.58T FREE 1.44T ( 91.4%) POOL testPool DEFSIZE 0 GC_START_THRESH 0 GC_STOP_THRESH 0 DEFPINTIME 0 PUT_RETENP 86400 FSS_POLICY maxfreespace GC_POLICY lru RS_POLICY fifo GID 2010 S_TYPE - CAPACITY 0 FREE 0 ( 0.0%) se2-gla.scotgrid.ac.uk /gridstorage CAPACITY 168.53G FREE 149.45G ( 88.7%) RDONLY
In this case, se2-gla is the DPM Head Node. pool1-gla and pool2-gla are DPM disk servers. The whole DPM consists of two pools, srmStore, which has 6 filesystems, and testPool, which has only 1. A number of the filesystems are currently marked read only, and note that testPool is reserved for a specific group (in this case dteam).