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authorJelmer Vernooij <jelmer@samba.org>2005-06-10 20:29:09 +0000
committerGerald W. Carter <jerry@samba.org>2008-04-23 08:46:44 -0500
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parentb82eb1abe3641a80ad6f431dd2fd625dc229eaed (diff)
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Large number of small fixes to the layout and the build system.
(This used to be commit 73fac0653c774a8ed8654b064fd63d4e486f6b0f)
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+<?xml version="1.0" encoding="iso-8859-1"?>
+<!DOCTYPE chapter PUBLIC "-//Samba-Team//DTD DocBook V4.2-Based Variant V1.0//EN" "http://www.samba.org/samba/DTD/samba-doc">
+<chapter id="largefile">
+<chapterinfo>
+ &author.jeremy;
+ &author.jht;
+ <pubdate>March 5, 2005</pubdate>
+</chapterinfo>
+<title>Handling Large Directories</title>
+
+<para>
+Samba-3.0.12 implements a solution for sites that have experienced performance degradation do to the
+problem of using Samba-3 with applications that need large numbers of files (100,000 or more) per directory.
+</para>
+
+<para>
+The key was fixing the directory handling to read only the current list requested instead of the old
+(up to samba-3.0.11) behaviour of reading the entire directory into memory before doling out names.
+Normally this would have broken OS/2 applications which have very strange delete semantics, but by
+stealing logic from Samba4 (thanks tridge) the current code in 3.0.12 handles this correctly.
+</para>
+
+<para>
+To set up an application that needs large number of files per directory in a way that does not
+damage performance unduly follow these steps:
+</para>
+
+<para>
+Firstly, you need to canonicalize all the files in the directory to have one case, upper or lower - take your
+pick (I chose upper as all my files were already upper case names). Then set up a new custom share for the
+application as follows:
+<screen>
+[bigshare]
+ path = /home/jeremy/tmp/manyfilesdir
+ read only = no
+ case sensitive = True
+ default case = upper
+ preserve case = no
+ short preserve case = no
+</screen>
+</para>
+
+<para>
+Of course, use your own path and settings, but set the case options to match the case of all the files in your
+directory. The path should point at the large directory needed for the application - any new files created in
+there and in any paths under it will be forced by smbd into upper case - but smbd will no longer have to scan
+the directory for names - it knows that if a file does not exist in upper case then it doesn't exist at all.
+</para>
+
+<para>
+The secret to this is really in the <smbconfoption name="case sensitive">True</smbconfoption>
+line. This tells smbd never to scan for case-insensitive versions of names. So if an application asks for a file
+called <filename>FOO</filename>, and it can not be found by a simple stat call, then smbd will return file not
+found immediately without scanning the containing directory for a version of a different case. The other
+<filename>xxx case xxx</filename> lines make this work by forcing a consistent case on all files created by smbd.
+</para>
+
+<para>
+Remember, all files and directories under the <parameter>path</parameter> directory must be in upper case
+with this &smb.conf; stanza as smbd will not be able to find lower case filenames with these settings. Also
+note this is done on a per-share basis, allowing this to be set only for a share servicing an application with
+this problematic behaviour (using large numbers of entries in a directory) - the rest of your smbd shares
+don't need to be affected.
+</para>
+
+<para>
+This makes smbd much faster when dealing with large directories. My test case has over 100,000 files and
+smbd now deals with this very efficiently.
+</para>
+
+</chapter>