Lines Matching refs:group
9 The layout of a standard block group is approximately as follows (each
33 For the special case of block group 0, the first 1024 bytes are unused,
40 The ext4 driver primarily works with the superblock and the group
41 descriptors that are found in block group 0. Redundant copies of the
42 superblock and group descriptors are written to some of the block groups
45 paragraph for more details). If the group does not have a redundant
46 copy, the block group begins with the data block bitmap. Note also that
48 GDT blockā space after the block group descriptors and before the start
57 As for the ordering of items in a block group, it is generally
58 established that the super block and the group descriptor table, if
59 present, will be at the beginning of the block group. The bitmaps and
70 logical block group; the bitmap spaces and the inode table space in the
71 first block group of the flex_bg are expanded to include the bitmaps
73 if the flex_bg size is 4, then group 0 will contain (in order) the
74 superblock, group descriptors, data block bitmaps for groups 0-3, inode
76 space in group 0 is for file data. The effect of this is to group the
77 block group metadata close together for faster loading, and to enable
79 and group descriptors are always at the beginning of block groups, even
86 Without the option META_BG, for safety concerns, all block group
87 descriptors copies are kept in the first block group. Given the default
88 128MiB(2^27 bytes) block group size and 64-byte group descriptors, ext4
92 The solution to this problem is to use the metablock group feature
95 groups. Each metablock group is a cluster of block groups whose group
97 filesystems with 4 KB block size, a single metablock group partition
98 includes 64 block groups, or 8 GiB of disk space. The metablock group
99 feature moves the location of the group descriptors from the congested
100 first block group of the whole filesystem into the first group of each
101 metablock group itself. The backups are in the second and last group of
102 each metablock group. This increases the 2^21 maximum block groups limit
106 the superblock is followed by a variable-length set of block group
107 descriptors. Instead, the superblock and a single block group descriptor
109 groups in a meta-block group. A meta-block group is a collection of
110 block groups which can be described by a single block group descriptor
111 block. Since the size of the block group descriptor structure is 64
112 bytes, a meta-block group contains 16 block groups for filesystems with
114 blocksize. Filesystems can either be created using this new block group
117 block group using this new layout.
125 A new feature for ext4 are three block group descriptor flags that
126 enable mkfs to skip initializing other parts of the block group
128 that the inode and block bitmaps for that group can be calculated and
130 generally the case for an empty block group or a block group containing
131 only fixed-location block group metadata. The INODE_ZEROED flag means