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Chapter 6. The replica Service (Replica Manager)

Table of Contents

The Basic Setup
Define a poolgroup for resilient pools
Operation
Pool States
Startup
Avoid replicas on the same host
Hybrid dCache
Commands for the admin interface
Properties of the replica service

The replica service (which is also referred to as Replica Manager) controls the number of replicas of a file on the pools. If no tertiary storage system is connected to a dCache instance (i.e., it is configured as a large file store), there might be only one copy of each file on disk. (At least the precious replica.) If a higher security and/or availability is required, the resilience feature of dCache can be used: If running in the default configuration, the replica service will make sure that the number of replicas of a file will be at least 2 and not more than 3. If only one replica is present it will be copied to another pool by a pool to pool transfer. If four or more replicas exist, some of them will be deleted.