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Oracle® ZFS Storage Appliance Administration Guide, Release OS8.7.x

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Updated: September 2017
 
 

Project vs. Share Replication

Although it is possible to configure remote replication on both the project level and share level, project-level replication is recommended for these reasons. The appliance allows administrators to configure remote replication on both the project and share level.

  • Replication snapshots are always taken at the project level. Multiple share level replications in a single project can create a substantial amount of overhead and consume space on the pool.

  • When reversing share-level replication, the share is placed in its own project. This means that replication reversals will end up splitting the share away from the other shares in the project, unless they are all replicated together.

Like other properties configurable on the Shares screen, each share can either inherit or override the configuration of its parent project. Inheriting the configuration means not only that the share is replicated on the same schedule to the same target with the same options as its parent project is, but also that the share will be replicated in the same stream using the same project-level snapshots as other shares inheriting the project's configuration. This may be important for applications which require consistency between data stored on multiple shares. Overriding the configuration means that the share will not be replicated with any project-level actions, though it may be replicated with its own share-level actions that will include the project. It is not possible to override part of the project's replication configuration and inherit the rest.

More precisely, the replication configuration of a project and its shares define some number of replication groups, each of which is replicated with a single stream using snapshots taken simultaneously. All groups contain the project itself (which essentially just includes its properties). One project-level group includes all shares inheriting the replication configuration of the parent project. Any share that overrides the project's configuration forms a new group consisting of only the project and the share itself.

For example, suppose you have:

  • A project home and shares bill, cindi, and dave.

  • home has replication configured with some number of actions.

  • home/bill and home/cindi inherit the project's replication configuration.

  • home/dave overrides the project's replication configuration, using its own configuration with some number of actions.

This configuration defines the following replication groups, each of which is replicated as a single stream per action using snapshots taken simultaneously on the project and shares:

  • One project-level group including home, home/bill, and home/cindi.

  • One share-level group including home and home/dave.


Note -  Due to current limitations, do not mix project- and share-level replications within the same project. This avoids unpredictable results when reversing the replication direction or when replicating clones. For more details, see Replication Packages and Cloning a Replication Package or Share.

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