Author: mdrob
Date: Tue Apr 22 15:24:32 2014
New Revision: 1589168
URL: http://svn.apache.org/r1589168
Log:
ACCUMULO-2710 Commit Alex's glossary updates
Modified:
accumulo/site/trunk/content/glossary.mdtext
Modified: accumulo/site/trunk/content/glossary.mdtext
URL:
http://svn.apache.org/viewvc/accumulo/site/trunk/content/glossary.mdtext?rev=1589168&r1=1589167&r2=1589168&view=diff
==============================================================================
--- accumulo/site/trunk/content/glossary.mdtext (original)
+++ accumulo/site/trunk/content/glossary.mdtext Tue Apr 22 15:24:32 2014
@@ -25,15 +25,15 @@ Notice: Licensed to the Apache Softwa
- **iterator** - a mechanism for modifying tablet-local portions of the
key/value space. Iterators are used for standard administrative tasks as well
as for custom processing.
- **iterator priority** - an iterator must be configured with a particular
scope and priority. When a tablet server enters that scope, it will
instantiate iterators in priority order starting from the smallest priority and
ending with the largest, and apply each to the data read before rewriting the
data or sending the data to the user.
- **iterator scopes** - the possible scopes for iterators are where the tablet
server is already reading and/or writing data: minor compaction / flush time
(*minc* scope), major compaction / file merging time (*majc* scope), and query
time (*scan* scope)
-- **gc** -
+- **gc** - process that identifies temporary files that are no longer needed
by any process, and deletes them.
- **key** - the key into the distributed sorted map which is accumulo. The
key is subdivided into row, column, and timestamp. The column is further
divided into family, qualifier, and visibility.
- **locality group** - a set of column families that will be grouped together
on disk. With no locality groups configured, data is stored on disk in row
order. If each column family were configured to be its own locality group, the
data for each column would be stored separately, in row order. Configuring
sets of columns into locality groups is a compromise between the two approaches
and will improve performance when multiple columns are accessed in the same
scan.
- **log-structured merge-tree** - the sorting / flushing / merging scheme on
which BigTable's design is based.
-- **logger** -
+- **logger** - in 1.4 and older, process that accepts updates to tablet
servers and writes them to local on-disk storage for redundancy. in 1.5 the
functionality was subsumed by the tablet server and datanode with HDFS writes.
- **major compaction** - merging multiple files into a single file. If all of
a tablet's files are merged into a single file, it is called a *full major
compaction*.
-- **master** -
+- **master** - process that detects and responds to tablet failures, balances
load across tablet servers by assigning and migrating tablets when required,
coordinates table operations, and handles tablet server logistics (startup,
shutdown, recovery).
- **minor compaction** - flushing data from memory to disk. Usually this
creates a new file for a tablet, but if the memory flushed is merge-sorted in
with data from an existing file (replacing that file), it is called a *merging
minor compaction*.
-- **monitor** -
+- **monitor** - process that displays status and usage information for all
Accumulo components.
- **permissions** - administrative abilities that must be given to a user such
as creating tables or users and changing permissions or configuration
parameters.
- **row** - the portion of the key that is controls atomicity. Keys with the
same row are guaranteed to remain on a single tablet hosted by a single tablet
server, therefore multiple key/value pairs can be added to or removed from a
row at the same time. The row is used for the primary sorting of the key.
- **scan** - reading a range of key/value pairs.
