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diff --git a/doc/rbd/rbd-replay.rst b/doc/rbd/rbd-replay.rst new file mode 100644 index 00000000..e1c96b21 --- /dev/null +++ b/doc/rbd/rbd-replay.rst @@ -0,0 +1,42 @@ +=================== + RBD Replay +=================== + +.. index:: Ceph Block Device; RBD Replay + +RBD Replay is a set of tools for capturing and replaying Rados Block Device +(RBD) workloads. To capture an RBD workload, ``lttng-tools`` must be installed +on the client, and ``librbd`` on the client must be the v0.87 (Giant) release +or later. To replay an RBD workload, ``librbd`` on the client must be the Giant +release or later. + +Capture and replay takes three steps: + +#. Capture the trace. Make sure to capture ``pthread_id`` context:: + + mkdir -p traces + lttng create -o traces librbd + lttng enable-event -u 'librbd:*' + lttng add-context -u -t pthread_id + lttng start + # run RBD workload here + lttng stop + +#. Process the trace with `rbd-replay-prep`_:: + + rbd-replay-prep traces/ust/uid/*/* replay.bin + +#. Replay the trace with `rbd-replay`_. Use read-only until you know + it's doing what you want:: + + rbd-replay --read-only replay.bin + +.. important:: ``rbd-replay`` will destroy data by default. Do not use against + an image you wish to keep, unless you use the ``--read-only`` option. + +The replayed workload does not have to be against the same RBD image or even the +same cluster as the captured workload. To account for differences, you may need +to use the ``--pool`` and ``--map-image`` options of ``rbd-replay``. + +.. _rbd-replay: ../../man/8/rbd-replay +.. _rbd-replay-prep: ../../man/8/rbd-replay-prep |