Notes on Ceph librados Client

Cluster Connection

• A client is an application that uses librados to connect to a Ceph cluster.

• It needs a cluster object populatd with cluster info (cluster name, info from ceph.conf)

• Then the client do a rados_connect and cluster handle is populated.

• A cluster handle can bind with different pools.

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Cluster IO context

• The I/O happens on a pool so the connection needs to bind to a pool.

• The connection to a pool gives the client an I/O context.

• The client only species an object name/xattr and librados maps it to a PG & OSD in the cluster.

• An obhect write to rados require key, value, and value size.

• librados::bufferlist is primarily used for storing object value.

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References

• http://docs.ceph.com/docs/luminous/rados/api/librados-intro/

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