Adding upstream version 14.2.21.upstream/14.2.21upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 42 insertions, 0 deletions

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+===================
+ 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