dCache - Enstore-org/enstore GitHub Wiki

Definition

DCache is a disk-based storage service, which can be configured to use Enstore for tape archival storage. This is the case at Fermilab, where it serves as the ingress/egress service for user data. It was developed at DESY, along with PNFS. Initially designed to be a provider of buffer space for tape storage systems, it has grown to offer pure disk storage capabilities as well. More information can be found at the dCache home page.

Configuration

Data stored in dCache is assigned to a pool which defines the storage requirements, such as replication count and storage class, for that data. Pools can be individually configured to archive data to tape or to retain all data on disk.

A dCache deployment typically consists of server nodes that provide interfaces to file transfer clients, and pool nodes that provide storage. Files are organized using a PNFS namespace, and tracked using PNFSID. As such, users cans use PNFSID explicitly to read/write files to dCache, but more typically interact via the POSIX-like namespace provided by PNFS.

File Transfer

Users may transfer files to/from dCache through gridftp, srm, xrootd, dcap, davix, … etc. In dCache terms, services are provided by “doors”.

DCache "flushes" (writes) data to and "restores" (reads) data from Enstore using encp, the client program for Enstore.