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Subject svn commit: r1459022 - in /accumulo/branches/1.5/docs/src/user_manual/chapters: design.tex table_configuration.tex
Date Wed, 20 Mar 2013 20:00:06 GMT
Author: kturner
Date: Wed Mar 20 20:00:05 2013
New Revision: 1459022

ACCUMULO-896 Added some info about automatic splitting to user manual.


Modified: accumulo/branches/1.5/docs/src/user_manual/chapters/design.tex
--- accumulo/branches/1.5/docs/src/user_manual/chapters/design.tex (original)
+++ accumulo/branches/1.5/docs/src/user_manual/chapters/design.tex Wed Mar 20 20:00:05 2013
@@ -62,12 +62,6 @@ TabletServers also perform recovery of a
 that was previously on a server that failed, reapplying any writes
 found in the write-ahead log to the tablet.
-The Loggers accept updates to Tablet servers and write them to local
-on-disk storage.  Each tablet server will write their updates to
-multiple loggers to preserve data in case of hardware failure.
 \subsection{Garbage Collector}
 Accumulo processes will share files stored in HDFS.  Periodically, the Garbage
@@ -129,6 +123,23 @@ by the Garbage Collector. This also prov
 remove deleted key-value pairs by omitting key-value pairs suppressed by a
 delete entry when the new file is created.
+When a table is created it has one tablet.  As the table grows its initial
+tablet eventually splits into two tablets.   Its likely that one of these
+tablets will migrate to another tablet server.  As the table continues to grow,
+its tablets will continue to split and be migrated.  The decision to
+automatically split a tablet is based on the size of a tablets files.   The
+size threshold at which a tablet splits is configurable per table.  In addition
+to automatic splitting, a user can manually add split points to a table to
+create new tablets.  Manually splitting a new table can parallelize reads and
+writes giving better initial performance without waiting for automatic
+As data is deleted from a table, tablets may shrink.  Over time this can lead
+to small or empty tablets.   To deal with this, merging of tablets was
+introduced in Accumulo 1.4.  This is discussed in more detail later.
 If a TabletServer fails, the Master detects it and automatically reassigns the tablets

Modified: accumulo/branches/1.5/docs/src/user_manual/chapters/table_configuration.tex
--- accumulo/branches/1.5/docs/src/user_manual/chapters/table_configuration.tex (original)
+++ accumulo/branches/1.5/docs/src/user_manual/chapters/table_configuration.tex Wed Mar 20
20:00:05 2013
@@ -703,4 +703,4 @@ splits, and logical time.  Tables are ex
 distcp command.  To export a table, it must be offline and stay offline while
 discp runs.  The reason it needs to stay offline is to prevent files from being
 deleted.  A table can be cloned and the clone taken offline inorder to avoid
-losing access to the table.  See docs/examples/README.example for an example.
+losing access to the table.  See docs/examples/README.export for an example.

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