Diskless replication documented inside example redis.conf.

redis.conf

@@ -240,6 +240,33 @@ slave-serve-stale-data yes
 # administrative / dangerous commands.
 slave-read-only yes
 
+# Replication SYNC strategy: disk or socket.
+#
+# New slaves and reconnecting slaves that are not able to continue the replication
+# process just receiving differences, need to do what is called a "full
+# synchronization". An RDB file is transmitted from the master to the slaves.
+# The transmission can happen in two different ways:
+#
+# 1) Disk-backed: The Redis master creates a new process that writes the RDB
+#                 file on disk. Later the file is transferred by the parent
+#                 process to the slaves incrementally.
+# 2) Diskless: The Redis master creates a new process that directly writes the
+#              RDB file to slave sockets, without touching the disk at all.
+#
+# With disk-backed replication, while the RDB file is generated, more slaves
+# can be queued and served with the RDB file as soon as the current child producing
+# the RDB file finishes its work. With diskless replication instead once
+# the transfer starts, new slaves arriving will be queued and a new transfer
+# will start when the current one terminates.
+#
+# When diskless replication is used, the master waits a configurable amount of
+# time (in seconds) before starting the transfer in the hope that multiple slaves
+# will arrive and the transfer can be parallelized.
+#
+# With slow disks and fast (large bandwidth) networks, diskless replication
+# works better.
+repl-diskless-sync no
+
 # Slaves send PINGs to server in a predefined interval. It's possible to change
 # this interval with the repl_ping_slave_period option. The default value is 10
 # seconds.