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diff --git a/doc/cephfs/experimental-features.rst b/doc/cephfs/experimental-features.rst new file mode 100644 index 000000000..ba60d12c7 --- /dev/null +++ b/doc/cephfs/experimental-features.rst @@ -0,0 +1,42 @@ +===================== +Experimental Features +===================== + +CephFS includes a number of experimental features which are not fully +stabilized or qualified for users to turn on in real deployments. We generally +do our best to clearly demarcate these and fence them off so they cannot be +used by mistake. + +Some of these features are closer to being done than others, though. We +describe each of them with an approximation of how risky they are and briefly +describe what is required to enable them. Note that doing so will +*irrevocably* flag maps in the monitor as having once enabled this flag to +improve debugging and support processes. + +Inline data +----------- +By default, all CephFS file data is stored in RADOS objects. The inline data +feature enables small files (generally <2KB) to be stored in the inode +and served out of the MDS. This may improve small-file performance but increases +load on the MDS. It is not sufficiently tested to support at this time, although +failures within it are unlikely to make non-inlined data inaccessible + +Inline data has always been off by default and requires setting +the ``inline_data`` flag. + +Inline data has been declared deprecated for the Octopus release, and will +likely be removed altogether in the Q release. + +Mantle: Programmable Metadata Load Balancer +------------------------------------------- + +Mantle is a programmable metadata balancer built into the MDS. The idea is to +protect the mechanisms for balancing load (migration, replication, +fragmentation) but stub out the balancing policies using Lua. For details, see +:doc:`/cephfs/mantle`. + +LazyIO +------ +LazyIO relaxes POSIX semantics. Buffered reads/writes are allowed even when a +file is opened by multiple applications on multiple clients. Applications are +responsible for managing cache coherency themselves. |