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Fix bug #398749 - Improve wording on inode calculation for smaller file systems

1 <?xml version='1.0' encoding="UTF-8"?>
2 <!-- $Header: /var/cvsroot/gentoo/xml/htdocs/doc/en/handbook/hb-install-filesystems.xml,v 1.9 2011/09/17 12:16:09 swift Exp $ -->
3 <!DOCTYPE included SYSTEM "/dtd/guide.dtd">
4
5 <included>
6
7 <version>8</version>
8 <date>2012-04-22</date>
9
10 <section id="filesystemsdesc">
11 <title>Filesystems</title>
12 <body>
13
14 <p test="contains('x86 Alpha',func:keyval('arch'))">
15 The Linux kernel supports various filesystems. We'll explain ext2, ext3, ext4,
16 ReiserFS, XFS and JFS as these are the most commonly used filesystems on Linux
17 systems.
18 </p>
19
20 <p test="func:keyval('arch')='IA64'">
21 The Linux kernel supports various filesystems. We'll explain vfat, ext2, ext3,
22 ext4, ReiserFS, XFS and JFS as these are the most commonly used filesystems on
23 Linux systems.
24 </p>
25
26 <p test="func:keyval('arch')='AMD64'">
27 Several filesystems are available. Some of them are found stable on the amd64
28 architecture, others aren't. The following filesystems are found to be stable:
29 ext2, ext3, ext4 and XFS. JFS and ReiserFS may work but need more testing. If
30 you're really adventurous you can try the other filesystems.
31 </p>
32
33 <p test="func:keyval('arch')='arm'">
34 Several filesystems are available. Some of them are found stable on the arm
35 architecture, others aren't. ext2, ext3 and ext4 are found to be stable. JFS,
36 XFS and ReiserFS may work but need more testing. If you're really adventurous
37 you can try the other filesystems.
38 </p>
39
40 <p test="func:keyval('arch')='HPPA'">
41 Several filesystems are available. Ext2, ext3, ext4, XFS and reiserfs are found
42 stable on the HPPA architecture. The others are very experimental.
43 </p>
44
45 <p test="func:keyval('arch')='MIPS'">
46 Several filesystems are available. ReiserFS, EXT2, EXT3 and EXT4 are found
47 stable on the MIPS architectures, others are experimental.
48 </p>
49
50 <p test="func:keyval('arch')='PPC'">
51 Several filesystems are available for use on the PowerPC architecture including
52 ext2, ext3, ReiserFS and XFS, each with their strengths and faults.
53 </p>
54
55 <note test="func:keyval('arch')='PPC64'">
56 Several filesystems are available. ext2, ext3 and ReiserFS support is built in
57 the Installation CD kernels. JFS and XFS support is available through kernel
58 modules.
59 </note>
60
61 <p test="func:keyval('arch')='SPARC'">
62 Several filesystems are available, some are known to be stable on the
63 SPARC architecture. Ext2, ext3 and ext4, for example, are known to work well.
64 Alternate filesystems may not function correctly.
65 </p>
66
67 <note test="func:keyval('arch')='Alpha'">
68 <c>aboot</c> only supports booting from <b>ext2</b> and <b>ext3</b>
69 partitions.
70 </note>
71
72 </body>
73 <body>
74
75 <p test="func:keyval('arch')='IA64'">
76 <b>vfat</b> is the MS-DOS filesystem, updated to allow long filenames. It is
77 also the only filesystem type that the EFI firmware on ia64 systems
78 understands. The boot partition on ia64 systems should always be vfat, but for
79 your data partitions you should use one of the other filesystems listed below.
80 </p>
81
82 <p>
83 <b>ext2</b> is the tried and true Linux filesystem but doesn't have metadata
84 journaling, which means that routine ext2 filesystem checks at startup time can
85 be quite time-consuming. There is now quite a selection of newer-generation
86 journaled filesystems that can be checked for consistency very quickly and are
87 thus generally preferred over their non-journaled counterparts. Journaled
88 filesystems prevent long delays when you boot your system and your filesystem
89 happens to be in an inconsistent state. If you intend to install Gentoo on a
90 very small disk (less than 4GB), then you'll need to tell ext2 to reserve enough
91 inodes when you create the filesystem. The <c>mke2fs</c> application uses the
92 "bytes-per-inode" setting to calculate how many inodes a file system should have.
93 By running <c>mke2fs -T small /dev/&lt;device&gt;</c> the number of inodes will
94 generally quadruple for a given file system as its "bytes-per-inode" reduces from
95 one every 16kB to one every 4kB. You can tune this even further by using
96 <c>mke2fs -i &lt;ratio&gt; /dev/&lt;device&gt;</c>.
97 </p>
98
99 <p>
100 <b>ext3</b> is the journaled version of the ext2 filesystem, providing metadata
101 journaling for fast recovery in addition to other enhanced journaling modes like
102 full data and ordered data journaling. It uses an HTree index that enables high
103 performance in almost all situations. In short, ext3 is a very good and
104 reliable filesystem. Ext3 is the recommended all-purpose all-platform
105 filesystem. If you intend to install Gentoo on a
106 very small disk (less than 4GB), then you'll need to tell ext2 to reserve enough
107 inodes when you create the filesystem. The <c>mke2fs</c> application uses the
108 "bytes-per-inode" setting to calculate how many inodes a file system should have.
109 By running <c>mke2fs -j -T small /dev/&lt;device&gt;</c> the number of inodes will
110 generally quadruple for a given file system as its "bytes-per-inode" reduces from
111 one every 16kB to one every 4kB. You can tune this even further by using
112 <c>mke2fs -j -i &lt;ratio&gt; /dev/&lt;device&gt;</c>.
113 </p>
114
115 <p test="contains('x86 Alpha MIPS AMD64 arm IA64 SPARC HPPA',func:keyval('arch'))">
116 <b>ext4</b> is a filesystem created as a fork of ext3 bringing new features,
117 performance improvements and removal of size limits with moderate changes
118 to the on-disk format. It can span volumes up to 1 EB and with maximum file
119 size of 16 TB. Instead of the classic ext2/3 bitmap block allocation ext4 uses
120 <uri link="http://en.wikipedia.org/wiki/Extent_%28file_systems%29">extents</uri>,
121 which improve large file performance and reduce fragmentation. Ext4 also provides
122 more sophisticated block allocation algorithms (delayed allocation and multiblock
123 allocation) giving the filesystem driver more ways to optimise the layout of data
124 on the disk. The ext4 filesystem is a compromise between production-grade code
125 stability and the desire to introduce extensions to an almost decade old
126 filesystem.
127 </p>
128
129 </body>
130 <body test="not(func:keyval('arch')='SPARC')">
131
132 <p test="not(func:keyval('arch')='PPC')">
133 <b>JFS</b> is IBM's high-performance journaling filesystem. JFS is a light,
134 fast and reliable B+tree-based filesystem with good performance in various
135 conditions.
136 </p>
137
138 <p>
139 <b>ReiserFS</b> is a B+tree-based journaled filesystem that has good overall
140 performance, especially when dealing with many tiny files at the cost of more
141 CPU cycles. ReiserFS appears to be less maintained than other filesystems.
142 </p>
143
144 <p>
145 <b>XFS</b> is a filesystem with metadata journaling which comes with a robust
146 feature-set and is optimized for scalability. XFS seems to be less forgiving to
147 various hardware problems.
148 </p>
149
150 </body>
151 </section>
152 </included>

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