diff --git a/src/main/docbkx/book.xml b/src/main/docbkx/book.xml
index cdfe5b2ca47..0234f85774c 100644
--- a/src/main/docbkx/book.xml
+++ b/src/main/docbkx/book.xml
@@ -2671,6 +2671,21 @@ ctime = Sat Jun 23 11:13:40 PDT 2012
+
+ Disabling the WAL
+ It is possible to disable the WAL, to improve performace in certain specific
+ situations. However, disabling the WAL puts your data at risk. The only situation where
+ this is recommended is during a bulk load. This is because, in the event of a problem,
+ the bulk load can be re-run with no risk of data loss.
+ The WAL is disabled by calling the HBase client field
+ Mutation.writeToWAL(false). Use the
+ Mutation.setDurability(Durability.SKIP_WAL) and Mutation.getDurability()
+ methods to set and get the field's value. There is no way to disable the WAL for only a
+ specific table.
+
+ If you disable the WAL for anything other than bulk loads, your data is at
+ risk.
+
diff --git a/src/main/docbkx/performance.xml b/src/main/docbkx/performance.xml
index 47b67be7621..57c866ad3a5 100644
--- a/src/main/docbkx/performance.xml
+++ b/src/main/docbkx/performance.xml
@@ -564,16 +564,17 @@ admin.createTable(table, splits);
HBase Client: Turn off WAL on Puts
- A frequently discussed option for increasing throughput on Puts
- is to call writeToWAL(false). Turning this off means that the RegionServer will
- not write the Put to the Write Ahead Log, only
- into the memstore, HOWEVER the consequence is that if there is a RegionServer failure
- there will be data loss. If writeToWAL(false) is used,
- do so with extreme caution. You may find in actuality that it makes little difference if
- your load is well distributed across the cluster.
+ A frequent request is to disable the WAL to increase performance of Puts. This is only
+ appropriate for bulk loads, as it puts your data at risk by removing the protection of the
+ WAL in the event of a region server crash. Bulk loads can be re-run in the event of a crash,
+ with little risk of data loss.
+
+ If you disable the WAL for anything other than bulk loads, your data is at
+ risk.In general, it is best to use WAL for Puts, and where loading throughput is a concern to
- use bulk loading techniques instead.
+ use bulk loading techniques instead. For normal
+ Puts, you are not likely to see a performance improvement which would outweigh the risk. To
+ disable the WAL, see .