From 343d4b0ddcfcf38c230053145e43f08fa10441b8 Mon Sep 17 00:00:00 2001
From: Mark Craig <mark.craig@forgerock.com>
Date: Wed, 30 Nov 2011 14:43:32 +0000
Subject: [PATCH] Added a footnote regarding the figure of 4x initial LDIF size for database growth on disk, see http://lists.forgerock.org/pipermail/opendj-dev/2011-November/001045.html
---
opendj3/src/main/docbkx/install-guide/chap-before-you-install.xml | 16 +++++++++++++++-
1 files changed, 15 insertions(+), 1 deletions(-)
diff --git a/opendj3/src/main/docbkx/install-guide/chap-before-you-install.xml b/opendj3/src/main/docbkx/install-guide/chap-before-you-install.xml
index a5f0c7b..8f2418a 100644
--- a/opendj3/src/main/docbkx/install-guide/chap-before-you-install.xml
+++ b/opendj3/src/main/docbkx/install-guide/chap-before-you-install.xml
@@ -64,7 +64,21 @@
the software and a small set of sample data. For installation in production,
read the rest of this section. You need at least 2 GB memory for OpenDJ and
4 times the disk space needed to house initial production data in LDIF
- format.</para>
+ format.<footnote>
+ <para>OpenDJ stores data in Berkeley DB Java Edition, which is implemented
+ as a rolling log. Berkeley DB appends updates to the end of the last log
+ file, and marks old pages as deleted. Berkeley DB cleaner threads monitor
+ the log file occupancy ratio, moving the data to get rid of old log files.
+ Yet, with the default occupancy ratio of 50%, log files are cleaned only
+ when they have less than 50% valid pages. As a result, the database can
+ reach twice its initial size in the worst case.</para>
+ <para>Furthermore, when you import data from LDIF, OpenDJ stores not only
+ the data, but also builds indexes for many of the attributes, resulting in
+ some growth. Replication historical data and other operational attributes
+ can also take up space.</para>
+ <para>Finally, it makes sense to leave space for growth in the database size
+ as you modify and add entries over time.</para></footnote>
+ </para>
<para>OpenDJ directory servers almost always benefit from having enough
system memory to cache all directory database files used. The reason
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