update cassandra.yaml comments post-CASSANDRA-10243

Jaumo · Jul 26, 2016 · 48a45ed · 48a45ed
1 parent 3d3359e
commit 48a45ed
Showing 1 changed file with 9 additions and 6 deletions.
diff --git a/conf/cassandra.yaml b/conf/cassandra.yaml
@@ -656,12 +656,15 @@ cross_node_timeout: false
 #   more than one replica on the same "rack" (which may not actually
 #   be a physical location)
 #
-# IF YOU CHANGE THE SNITCH AFTER DATA IS INSERTED INTO THE CLUSTER,
-# YOU MUST RUN A FULL REPAIR, SINCE THE SNITCH AFFECTS WHERE REPLICAS
-# ARE PLACED.
-#
-# IF THE RACK A REPLICA IS PLACED IN CHANGES AFTER THE REPLICA HAS BEEN
-# ADDED TO A RING, THE NODE MUST BE DECOMMISSIONED AND REBOOTSTRAPPED.
+# CASSANDRA WILL NOT ALLOW YOU TO SWITCH TO AN INCOMPATIBLE SNITCH
+# ONCE DATA IS INSERTED INTO THE CLUSTER.  This would cause data loss.
+# This means that if you start with the default SimpleSnitch, which
+# locates every node on "rack1" in "datacenter1", your only options
+# if you need to add another datacenter are GossipingPropertyFileSnitch
+# (and the older PFS).  From there, if you want to migrate to an
+# incompatible snitch like Ec2Snitch you can do it by adding new nodes
+# under Ec2Snitch (which will locate them in a new "datacenter") and
+# decommissioning the old ones.
 #
 # Out of the box, Cassandra provides
 #  - SimpleSnitch: