minor #9495 Specify how provide a high availability (jderusse, javiereguiluz)

This PR was merged into the 3.4 branch.

Discussion
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Specify how provide a high availability

Fixes symfony/symfony#26026

Commits
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2d8e18b Reword
bd5a472 Specify how provide a high availability

Author: javiereguiluz

components/lock.rst

@@ -260,6 +260,13 @@ Instead of the simple majority strategy (``ConsensusStrategy``) an
 ``UnanimousStrategy`` can be used to require the lock to be acquired in all
 the stores.
 
+.. caution::
+
+    In order to get high availability when using the ``ConsensusStrategy``, the
+    minimum cluster size must be three servers. This allows the cluster to keep
+    working when a single server fails (because this strategy requires that the
+    lock is acquired in more than half of the servers).
+
 Reliability
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