Increase default CL space to 8GB

patch by Benedict Elliott Smith; tested by Ryan McGuire and reviewed by jbellis for CASSANDRA-7031

CHANGES.txt

@@ -1,4 +1,5 @@
 2.1.0-beta2
+ * Increase default CL space to 8GB (CASSANDRA-7031)
  * Add range tombstones to read repair digests (CASSANDRA-6863)
  * Fix BTree.clear for large updates (CASSANDRA-6943)
  * Fail write instead of logging a warning when unable to append to CL

conf/cassandra.yaml

@@ -287,13 +287,13 @@ memtable_allocation_type: heap_buffers
 
 # Total space to use for commitlogs.  Since commitlog segments are
 # mmapped, and hence use up address space, the default size is 32
-# on 32-bit JVMs, and 1024 on 64-bit JVMs.
+# on 32-bit JVMs, and 8192 on 64-bit JVMs.
 #
 # If space gets above this value (it will round up to the next nearest
 # segment multiple), Cassandra will flush every dirty CF in the oldest
 # segment and remove it.  So a small total commitlog space will tend
 # to cause more flush activity on less-active columnfamilies.
-# commitlog_total_space_in_mb: 4096
+# commitlog_total_space_in_mb: 8192
 
 # This sets the amount of memtable flush writer threads.  These will
 # be blocked by disk io, and each one will hold a memtable in memory

src/java/org/apache/cassandra/config/DatabaseDescriptor.java

@@ -187,7 +187,7 @@ public class DatabaseDescriptor
         }
 
         if (conf.commitlog_total_space_in_mb == null)
-            conf.commitlog_total_space_in_mb = hasLargeAddressSpace() ? 1024 : 32;
+            conf.commitlog_total_space_in_mb = hasLargeAddressSpace() ? 8192 : 32;
 
         /* evaluate the DiskAccessMode Config directive, which also affects indexAccessMode selection */
         if (conf.disk_access_mode == Config.DiskAccessMode.auto)