HBASE-20349 [DOC] upgrade guide should call out removal of prefix-tree data 
block encoding

Project: http://git-wip-us.apache.org/repos/asf/hbase/repo
Commit: http://git-wip-us.apache.org/repos/asf/hbase/commit/d14a7ff1
Tree: http://git-wip-us.apache.org/repos/asf/hbase/tree/d14a7ff1
Diff: http://git-wip-us.apache.org/repos/asf/hbase/diff/d14a7ff1

Branch: refs/heads/HBASE-19064
Commit: d14a7ff1876d68aab3d019b5179a7eff8f3e2356
Parents: c4ebf66
Author: Michael Stack <st...@apache.org>
Authored: Wed Apr 11 15:07:27 2018 -0700
Committer: Michael Stack <st...@apache.org>
Committed: Thu Apr 12 04:32:46 2018 -0700

 src/main/asciidoc/_chapters/troubleshooting.adoc |  4 ++--
 src/main/asciidoc/_chapters/upgrading.adoc       | 11 +++++++++++
 2 files changed, 13 insertions(+), 2 deletions(-)

diff --git a/src/main/asciidoc/_chapters/troubleshooting.adoc 
index 83f1989..52c0860 100644
--- a/src/main/asciidoc/_chapters/troubleshooting.adoc
+++ b/src/main/asciidoc/_chapters/troubleshooting.adoc
@@ -102,9 +102,9 @@ To disable, set the logging level back to `INFO` level.
 === JVM Garbage Collection Logs
 All example Garbage Collection logs in this section are based on Java 8 
output. The introduction of Unified Logging in Java 9 and newer will result in 
very different looking logs.
 HBase is memory intensive, and using the default GC you can see long pauses in 
all threads including the _Juliet Pause_ aka "GC of Death". To help debug this 
or confirm this is happening GC logging can be turned on in the Java virtual 

diff --git a/src/main/asciidoc/_chapters/upgrading.adoc 
index 0c7edcc..046fc90 100644
--- a/src/main/asciidoc/_chapters/upgrading.adoc
+++ b/src/main/asciidoc/_chapters/upgrading.adoc
@@ -409,6 +409,17 @@ A brief summary of related changes:
 The Distributed Log Replay feature was broken and has been removed from HBase 
2.y+. As a consequence all related configs, metrics, RPC fields, and logging 
have also been removed. Note that this feature was found to be unreliable in 
the run up to HBase 1.0, defaulted to being unused, and was effectively removed 
in HBase 1.2.0 when we started ignoring the config that turns it on 
(link:https://issues.apache.org/jira/browse/HBASE-14465[HBASE-14465]). If you 
are currently using the feature, be sure to perform a clean shutdown, ensure 
all DLR work is complete, and disable the feature prior to upgrading.
+._prefix-tree_ encoding removed
+The prefix-tree encoding was removed from HBase 2.0.0 
+It was (late!) deprecated in hbase-1.2.7, hbase-1.4.0, and hbase-1.3.2.
+This feature was removed because it as not being actively maintained. If 
interested in reviving this
+sweet facility which improved random read latencies at the expensive of slowed 
+write the HBase developers list at _dev at hbase dot apache dot org_.
 .Changed metrics

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