diff --git a/doc/source/overview_erasure_code.rst b/doc/source/overview_erasure_code.rst index d1b1a5d6a9..a8a8e87891 100755 --- a/doc/source/overview_erasure_code.rst +++ b/doc/source/overview_erasure_code.rst @@ -251,9 +251,22 @@ of them will be made of parity data (calculations depending on ec_type). When deciding which devices to use in the EC policy's object ring, be sure to carefully consider the performance impacts. Running some performance benchmarking in a test environment for your configuration is highly recommended -before deployment. Once you have configured your EC policy in `swift.conf` and -created your object ring, your application is ready to start using EC simply by -creating a container with the specified policy name and interacting as usual. +before deployment. + +To create the EC policy's object ring, the only difference in the usage of the +``swift-ring-builder create`` command is the ``replicas`` parameter. The +``replicas`` value is the number of fragments spread across the object servers +associated with the ring; ``replicas`` must be equal to the sum of +``ec_num_data_fragments`` and ``ec_num_parity_fragments``. For example:: + + swift-ring-builder object-1.builder create 10 14 1 + +Note that in this example the ``replicas`` value of 14 is based on the sum of +10 EC data fragments and 4 EC parity fragments. + +Once you have configured your EC policy in `swift.conf` and created your object +ring, your application is ready to start using EC simply by creating a container +with the specified policy name and interacting as usual. .. note::