Update compaction_throughput_mb_per_sec default from 16 to 64

patch by Jeremy Hanna; reviewed by Mick Semb Wever for CASSANDRA-14902

CHANGES.txt

@@ -1,4 +1,5 @@
 4.0-alpha5
+ * Update compaction_throughput_mb_per_sec throttle default to 64 (CASSANDRA-14902)
  * Add option to disable compaction at startup (CASSANDRA-15927)
  * FBUtilities.getJustLocalAddress falls back to lo ip on misconfigured nodes (CASSANDRA-15901)
  * Close channel and reduce buffer allocation during entire sstable streaming with SSL (CASSANDRA-15900)

NEWS.txt

@@ -251,6 +251,8 @@ Upgrading
       four digits need to be prefixed with a plus or minus sign.
     - cqlsh now returns a non-zero code in case of errors. This is a backward incompatible change so it may
       break existing scripts that rely on the current behavior. See CASSANDRA-15623 for more details.
+    - Updated the default compaction_throughput_mb_per_sec to to 64. The original
+      default (16) was meant for spinning disk volumes.  See CASSANDRA-14902 for details.
 
 
 Deprecation

conf/cassandra.yaml

@@ -831,9 +831,10 @@ concurrent_materialized_view_builders: 1
 # system. The faster you insert data, the faster you need to compact in
 # order to keep the sstable count down, but in general, setting this to
 # 16 to 32 times the rate you are inserting data is more than sufficient.
-# Setting this to 0 disables throttling. Note that this account for all types
-# of compaction, including validation compaction.
-compaction_throughput_mb_per_sec: 16
+# Setting this to 0 disables throttling. Note that this accounts for all types
+# of compaction, including validation compaction (building Merkle trees
+# for repairs).
+compaction_throughput_mb_per_sec: 64
 
 # When compacting, the replacement sstable(s) can be opened before they
 # are completely written, and used in place of the prior sstables for