.. SPDX-License-Identifier: GPL-2.0 Blocks ------ ext4 allocates storage space in units of “blocks”. A block is a group of sectors between 1KiB and 64KiB, and the number of sectors must be an integral power of 2. Blocks are in turn grouped into larger units called block groups. Block size is specified at mkfs time and typically is 4KiB. You may experience mounting problems if block size is greater than page size (i.e. 64KiB blocks on a i386 which only has 4KiB memory pages). By default a filesystem can contain 2^32 blocks; if the '64bit' feature is enabled, then a filesystem can have 2^64 blocks. For 32-bit filesystems, limits are as follows: .. list-table:: :widths: 1 1 1 1 1 :header-rows: 1 * - Item - 1KiB - 2KiB - 4KiB - 64KiB * - Blocks - 2^32 - 2^32 - 2^32 - 2^32 * - Inodes - 2^32 - 2^32 - 2^32 - 2^32 * - File System Size - 4TiB - 8TiB - 16TiB - 256PiB * - Blocks Per Block Group - 8,192 - 16,384 - 32,768 - 524,288 * - Inodes Per Block Group - 8,192 - 16,384 - 32,768 - 524,288 * - Block Group Size - 8MiB - 32MiB - 128MiB - 32GiB * - Blocks Per File, Extents - 2^32 - 2^32 - 2^32 - 2^32 * - Blocks Per File, Block Maps - 16,843,020 - 134,480,396 - 1,074,791,436 - 4,398,314,962,956 (really 2^32 due to field size limitations) * - File Size, Extents - 4TiB - 8TiB - 16TiB - 256TiB * - File Size, Block Maps - 16GiB - 256GiB - 4TiB - 256TiB For 64-bit filesystems, limits are as follows: .. list-table:: :widths: 1 1 1 1 1 :header-rows: 1 * - Item - 1KiB - 2KiB - 4KiB - 64KiB * - Blocks - 2^64 - 2^64 - 2^64 - 2^64 * - Inodes - 2^32 - 2^32 - 2^32 - 2^32 * - File System Size - 16ZiB - 32ZiB - 64ZiB - 1YiB * - Blocks Per Block Group - 8,192 - 16,384 - 32,768 - 524,288 * - Inodes Per Block Group - 8,192 - 16,384 - 32,768 - 524,288 * - Block Group Size - 8MiB - 32MiB - 128MiB - 32GiB * - Blocks Per File, Extents - 2^32 - 2^32 - 2^32 - 2^32 * - Blocks Per File, Block Maps - 16,843,020 - 134,480,396 - 1,074,791,436 - 4,398,314,962,956 (really 2^32 due to field size limitations) * - File Size, Extents - 4TiB - 8TiB - 16TiB - 256TiB * - File Size, Block Maps - 16GiB - 256GiB - 4TiB - 256TiB Note: Files not using extents (i.e. files using block maps) must be placed within the first 2^32 blocks of a filesystem. Files with extents must be placed within the first 2^48 blocks of a filesystem. It's not clear what happens with larger filesystems.