doc/garage.md

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+# Garage
+
+Our S3-compatible object storage service is based on [Garage][1].
+
+Garage is running as a cluster, with one VM each on 3 different physical hosts
+in 2 different zones (data centers).
+
+Replication mode is set to "2", meaning PUTs are always immediately synced to
+nodes in 2 different zones (write/read consistency guaranteed by default).
+
+When all nodes in one zone become unavailable, the cluster is switching to
+read-only mode automatically, since the write quorum cannot be reached in that
+case. If it is necessary (in an emergency) to write to nodes in only one zone,
+you can change the replication mode to "2-dangerous", which lowers the write
+quorum to 1.
+
+Please refer to the [replication documentation][2] for more detailed information.
+
+[1]: https://garagehq.deuxfleurs.fr
+[2]: https://garagehq.deuxfleurs.fr/documentation/reference-manual/configuration/#replication-mode