1 .. SPDX-License-Identifier: GPL-2.0 1 .. SPDX-License-Identifier: GPL-2.0
2 2
3 Blocks 3 Blocks
4 ------ 4 ------
5 5
6 ext4 allocates storage space in units of “bl 6 ext4 allocates storage space in units of “blocks”. A block is a group of
7 sectors between 1KiB and 64KiB, and the number 7 sectors between 1KiB and 64KiB, and the number of sectors must be an
8 integral power of 2. Blocks are in turn groupe 8 integral power of 2. Blocks are in turn grouped into larger units called
9 block groups. Block size is specified at mkfs 9 block groups. Block size is specified at mkfs time and typically is
10 4KiB. You may experience mounting problems if 10 4KiB. You may experience mounting problems if block size is greater than
11 page size (i.e. 64KiB blocks on a i386 which o 11 page size (i.e. 64KiB blocks on a i386 which only has 4KiB memory
12 pages). By default a filesystem can contain 2^ 12 pages). By default a filesystem can contain 2^32 blocks; if the '64bit'
13 feature is enabled, then a filesystem can have !! 13 feature is enabled, then a filesystem can have 2^64 blocks.
14 of structures is stored in terms of the block <<
15 in and not the absolute offset on disk. <<
16 14
17 For 32-bit filesystems, limits are as follows: 15 For 32-bit filesystems, limits are as follows:
18 16
19 .. list-table:: 17 .. list-table::
20 :widths: 1 1 1 1 1 18 :widths: 1 1 1 1 1
21 :header-rows: 1 19 :header-rows: 1
22 20
23 * - Item 21 * - Item
24 - 1KiB 22 - 1KiB
25 - 2KiB 23 - 2KiB
26 - 4KiB 24 - 4KiB
27 - 64KiB 25 - 64KiB
28 * - Blocks 26 * - Blocks
29 - 2^32 27 - 2^32
30 - 2^32 28 - 2^32
31 - 2^32 29 - 2^32
32 - 2^32 30 - 2^32
33 * - Inodes 31 * - Inodes
34 - 2^32 32 - 2^32
35 - 2^32 33 - 2^32
36 - 2^32 34 - 2^32
37 - 2^32 35 - 2^32
38 * - File System Size 36 * - File System Size
39 - 4TiB 37 - 4TiB
40 - 8TiB 38 - 8TiB
41 - 16TiB 39 - 16TiB
42 - 256TiB !! 40 - 256PiB
43 * - Blocks Per Block Group 41 * - Blocks Per Block Group
44 - 8,192 42 - 8,192
45 - 16,384 43 - 16,384
46 - 32,768 44 - 32,768
47 - 524,288 45 - 524,288
48 * - Inodes Per Block Group 46 * - Inodes Per Block Group
49 - 8,192 47 - 8,192
50 - 16,384 48 - 16,384
51 - 32,768 49 - 32,768
52 - 524,288 50 - 524,288
53 * - Block Group Size 51 * - Block Group Size
54 - 8MiB 52 - 8MiB
55 - 32MiB 53 - 32MiB
56 - 128MiB 54 - 128MiB
57 - 32GiB 55 - 32GiB
58 * - Blocks Per File, Extents 56 * - Blocks Per File, Extents
59 - 2^32 57 - 2^32
60 - 2^32 58 - 2^32
61 - 2^32 59 - 2^32
62 - 2^32 60 - 2^32
63 * - Blocks Per File, Block Maps 61 * - Blocks Per File, Block Maps
64 - 16,843,020 62 - 16,843,020
65 - 134,480,396 63 - 134,480,396
66 - 1,074,791,436 64 - 1,074,791,436
67 - 4,398,314,962,956 (really 2^32 due to f 65 - 4,398,314,962,956 (really 2^32 due to field size limitations)
68 * - File Size, Extents 66 * - File Size, Extents
69 - 4TiB 67 - 4TiB
70 - 8TiB 68 - 8TiB
71 - 16TiB 69 - 16TiB
72 - 256TiB 70 - 256TiB
73 * - File Size, Block Maps 71 * - File Size, Block Maps
74 - 16GiB 72 - 16GiB
75 - 256GiB 73 - 256GiB
76 - 4TiB 74 - 4TiB
77 - 256TiB 75 - 256TiB
78 76
79 For 64-bit filesystems, limits are as follows: 77 For 64-bit filesystems, limits are as follows:
80 78
81 .. list-table:: 79 .. list-table::
82 :widths: 1 1 1 1 1 80 :widths: 1 1 1 1 1
83 :header-rows: 1 81 :header-rows: 1
84 82
85 * - Item 83 * - Item
86 - 1KiB 84 - 1KiB
87 - 2KiB 85 - 2KiB
88 - 4KiB 86 - 4KiB
89 - 64KiB 87 - 64KiB
90 * - Blocks 88 * - Blocks
91 - 2^64 89 - 2^64
92 - 2^64 90 - 2^64
93 - 2^64 91 - 2^64
94 - 2^64 92 - 2^64
95 * - Inodes 93 * - Inodes
96 - 2^32 94 - 2^32
97 - 2^32 95 - 2^32
98 - 2^32 96 - 2^32
99 - 2^32 97 - 2^32
100 * - File System Size 98 * - File System Size
101 - 16ZiB 99 - 16ZiB
102 - 32ZiB 100 - 32ZiB
103 - 64ZiB 101 - 64ZiB
104 - 1YiB 102 - 1YiB
105 * - Blocks Per Block Group 103 * - Blocks Per Block Group
106 - 8,192 104 - 8,192
107 - 16,384 105 - 16,384
108 - 32,768 106 - 32,768
109 - 524,288 107 - 524,288
110 * - Inodes Per Block Group 108 * - Inodes Per Block Group
111 - 8,192 109 - 8,192
112 - 16,384 110 - 16,384
113 - 32,768 111 - 32,768
114 - 524,288 112 - 524,288
115 * - Block Group Size 113 * - Block Group Size
116 - 8MiB 114 - 8MiB
117 - 32MiB 115 - 32MiB
118 - 128MiB 116 - 128MiB
119 - 32GiB 117 - 32GiB
120 * - Blocks Per File, Extents 118 * - Blocks Per File, Extents
121 - 2^32 119 - 2^32
122 - 2^32 120 - 2^32
123 - 2^32 121 - 2^32
124 - 2^32 122 - 2^32
125 * - Blocks Per File, Block Maps 123 * - Blocks Per File, Block Maps
126 - 16,843,020 124 - 16,843,020
127 - 134,480,396 125 - 134,480,396
128 - 1,074,791,436 126 - 1,074,791,436
129 - 4,398,314,962,956 (really 2^32 due to f 127 - 4,398,314,962,956 (really 2^32 due to field size limitations)
130 * - File Size, Extents 128 * - File Size, Extents
131 - 4TiB 129 - 4TiB
132 - 8TiB 130 - 8TiB
133 - 16TiB 131 - 16TiB
134 - 256TiB 132 - 256TiB
135 * - File Size, Block Maps 133 * - File Size, Block Maps
136 - 16GiB 134 - 16GiB
137 - 256GiB 135 - 256GiB
138 - 4TiB 136 - 4TiB
139 - 256TiB 137 - 256TiB
140 138
141 Note: Files not using extents (i.e. files usin 139 Note: Files not using extents (i.e. files using block maps) must be
142 placed within the first 2^32 blocks of a files 140 placed within the first 2^32 blocks of a filesystem. Files with extents
143 must be placed within the first 2^48 blocks of 141 must be placed within the first 2^48 blocks of a filesystem. It's not
144 clear what happens with larger filesystems. 142 clear what happens with larger filesystems.
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