diff --git a/src/docbkx/book.xml b/src/docbkx/book.xml
index 271313e4c41..9d016143f7f 100644
--- a/src/docbkx/book.xml
+++ b/src/docbkx/book.xml
@@ -1009,6 +1009,33 @@ to ensure well-formedness of your document after an edit session.
with configuration such as this.
+ hbase.regionserver.handler.count
+
+ This setting defines the number of threads that are kept open to answer
+ incoming requests to user tables. The default of 10 is rather low in order to
+ prevent users from killing their region servers when using large write buffers
+ with a high number of concurrent clients. The rule of thumb is to keep this
+ number low when the payload per request approaches the MB (big puts, scans using
+ a large cache) and high when the payload is small (gets, small puts, ICVs, deletes).
+
+
+ It is safe to set that number to the
+ maximum number of incoming clients if their payload is small, the typical example
+ being a cluster that serves a website since puts aren't typically buffered
+ and most of the operations are gets.
+
+
+ The reason why it is dangerous to keep this setting high is that the aggregate
+ size of all the puts that are currently happening in a region server may impose
+ too much pressure on its memory, or even trigger an OutOfMemoryError. A region server
+ running on low memory will trigger its JVM's garbage collector to run more frequently
+ up to a point where GC pauses become noticeable (the reason being that all the memory
+ used to keep all the requests' payloads cannot be trashed, no matter how hard the
+ garbage collector tries). After some time, the overall cluster
+ throughput is affected since every request that hits that region server will take longer,
+ which exacerbates the problem even more.
+
+
Configuration for large memory machines