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. The location
14 of structures is stored in terms of the block 14 of structures is stored in terms of the block number the structure lives
15 in and not the absolute offset on disk. 15 in and not the absolute offset on disk.
16 16
17 For 32-bit filesystems, limits are as follows: 17 For 32-bit filesystems, limits are as follows:
18 18
19 .. list-table:: 19 .. list-table::
20 :widths: 1 1 1 1 1 20 :widths: 1 1 1 1 1
21 :header-rows: 1 21 :header-rows: 1
22 22
23 * - Item 23 * - Item
24 - 1KiB 24 - 1KiB
25 - 2KiB 25 - 2KiB
26 - 4KiB 26 - 4KiB
27 - 64KiB 27 - 64KiB
28 * - Blocks 28 * - Blocks
29 - 2^32 29 - 2^32
30 - 2^32 30 - 2^32
31 - 2^32 31 - 2^32
32 - 2^32 32 - 2^32
33 * - Inodes 33 * - Inodes
34 - 2^32 34 - 2^32
35 - 2^32 35 - 2^32
36 - 2^32 36 - 2^32
37 - 2^32 37 - 2^32
38 * - File System Size 38 * - File System Size
39 - 4TiB 39 - 4TiB
40 - 8TiB 40 - 8TiB
41 - 16TiB 41 - 16TiB
42 - 256TiB 42 - 256TiB
43 * - Blocks Per Block Group 43 * - Blocks Per Block Group
44 - 8,192 44 - 8,192
45 - 16,384 45 - 16,384
46 - 32,768 46 - 32,768
47 - 524,288 47 - 524,288
48 * - Inodes Per Block Group 48 * - Inodes Per Block Group
49 - 8,192 49 - 8,192
50 - 16,384 50 - 16,384
51 - 32,768 51 - 32,768
52 - 524,288 52 - 524,288
53 * - Block Group Size 53 * - Block Group Size
54 - 8MiB 54 - 8MiB
55 - 32MiB 55 - 32MiB
56 - 128MiB 56 - 128MiB
57 - 32GiB 57 - 32GiB
58 * - Blocks Per File, Extents 58 * - Blocks Per File, Extents
59 - 2^32 59 - 2^32
60 - 2^32 60 - 2^32
61 - 2^32 61 - 2^32
62 - 2^32 62 - 2^32
63 * - Blocks Per File, Block Maps 63 * - Blocks Per File, Block Maps
64 - 16,843,020 64 - 16,843,020
65 - 134,480,396 65 - 134,480,396
66 - 1,074,791,436 66 - 1,074,791,436
67 - 4,398,314,962,956 (really 2^32 due to f 67 - 4,398,314,962,956 (really 2^32 due to field size limitations)
68 * - File Size, Extents 68 * - File Size, Extents
69 - 4TiB 69 - 4TiB
70 - 8TiB 70 - 8TiB
71 - 16TiB 71 - 16TiB
72 - 256TiB 72 - 256TiB
73 * - File Size, Block Maps 73 * - File Size, Block Maps
74 - 16GiB 74 - 16GiB
75 - 256GiB 75 - 256GiB
76 - 4TiB 76 - 4TiB
77 - 256TiB 77 - 256TiB
78 78
79 For 64-bit filesystems, limits are as follows: 79 For 64-bit filesystems, limits are as follows:
80 80
81 .. list-table:: 81 .. list-table::
82 :widths: 1 1 1 1 1 82 :widths: 1 1 1 1 1
83 :header-rows: 1 83 :header-rows: 1
84 84
85 * - Item 85 * - Item
86 - 1KiB 86 - 1KiB
87 - 2KiB 87 - 2KiB
88 - 4KiB 88 - 4KiB
89 - 64KiB 89 - 64KiB
90 * - Blocks 90 * - Blocks
91 - 2^64 91 - 2^64
92 - 2^64 92 - 2^64
93 - 2^64 93 - 2^64
94 - 2^64 94 - 2^64
95 * - Inodes 95 * - Inodes
96 - 2^32 96 - 2^32
97 - 2^32 97 - 2^32
98 - 2^32 98 - 2^32
99 - 2^32 99 - 2^32
100 * - File System Size 100 * - File System Size
101 - 16ZiB 101 - 16ZiB
102 - 32ZiB 102 - 32ZiB
103 - 64ZiB 103 - 64ZiB
104 - 1YiB 104 - 1YiB
105 * - Blocks Per Block Group 105 * - Blocks Per Block Group
106 - 8,192 106 - 8,192
107 - 16,384 107 - 16,384
108 - 32,768 108 - 32,768
109 - 524,288 109 - 524,288
110 * - Inodes Per Block Group 110 * - Inodes Per Block Group
111 - 8,192 111 - 8,192
112 - 16,384 112 - 16,384
113 - 32,768 113 - 32,768
114 - 524,288 114 - 524,288
115 * - Block Group Size 115 * - Block Group Size
116 - 8MiB 116 - 8MiB
117 - 32MiB 117 - 32MiB
118 - 128MiB 118 - 128MiB
119 - 32GiB 119 - 32GiB
120 * - Blocks Per File, Extents 120 * - Blocks Per File, Extents
121 - 2^32 121 - 2^32
122 - 2^32 122 - 2^32
123 - 2^32 123 - 2^32
124 - 2^32 124 - 2^32
125 * - Blocks Per File, Block Maps 125 * - Blocks Per File, Block Maps
126 - 16,843,020 126 - 16,843,020
127 - 134,480,396 127 - 134,480,396
128 - 1,074,791,436 128 - 1,074,791,436
129 - 4,398,314,962,956 (really 2^32 due to f 129 - 4,398,314,962,956 (really 2^32 due to field size limitations)
130 * - File Size, Extents 130 * - File Size, Extents
131 - 4TiB 131 - 4TiB
132 - 8TiB 132 - 8TiB
133 - 16TiB 133 - 16TiB
134 - 256TiB 134 - 256TiB
135 * - File Size, Block Maps 135 * - File Size, Block Maps
136 - 16GiB 136 - 16GiB
137 - 256GiB 137 - 256GiB
138 - 4TiB 138 - 4TiB
139 - 256TiB 139 - 256TiB
140 140
141 Note: Files not using extents (i.e. files usin 141 Note: Files not using extents (i.e. files using block maps) must be
142 placed within the first 2^32 blocks of a files 142 placed within the first 2^32 blocks of a filesystem. Files with extents
143 must be placed within the first 2^48 blocks of 143 must be placed within the first 2^48 blocks of a filesystem. It's not
144 clear what happens with larger filesystems. 144 clear what happens with larger filesystems.
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