inode/block/superblock/inode bitmap/block bitmap
inode记录文件的权限与属性,block记录文件的实际内容。
每个inode大小固定为128bytes,block大小为1k,2k,或4k。
每个文件仅会占用一个inode,每个block内最多放一个文件的数据,如果文件大于block的大小,则一个文件会占用多个block,如果文件小于block的大小,则该block的剩余空间被浪费了。
查找文件路径是先找inode,然后找inode对应的block。inode记录一个block会花掉4bytes。
[[email protected] ~]# df
Filesystem 1K-blocks Used Available Use% Mounted on
/dev/xvda 20151324 10859244 8269764 57% /
tmpfs 254444 0 254444 0% /dev/shm
上图发现,linode的文件系统格式化后默认的block大小是1K。
[[email protected] ~]# dumpe2fs /dev/xvda -h
dumpe2fs 1.39 (29-May-2006)
Filesystem volume name: <none>
Last mounted on: <not available>
Filesystem UUID: 4bec49da-617a-4c45-9909-7dbc1d3cad36
Filesystem magic number: 0xEF53
Filesystem revision #: 1 (dynamic)
Filesystem features: has_journal ext_attr resize_inode dir_index filetype needs_recovery sparse_super large_file
Default mount options: (none)
Filesystem state: clean (此文件系统是没有问题的。)
Errors behavior: Continue
Filesystem OS type: Linux
Inode count: 1178112 (inode的总数)
Block count: 5111808 (block的总数)
Reserved block count: 255579
Free blocks: 4876817 (还有多少个block可用)
Free inodes: 1150569 (还有多少个inode可用)
First block: 0
Block size: 4096 (每个block的大小为4K)
Fragment size: 4096
Reserved GDT blocks: 43
Blocks per group: 32768
Fragments per group: 32768
Inodes per group: 7552
Inode blocks per group: 472
Filesystem created: Wed Apr 20 15:36:05 2011
Last mount time: Tue Aug 7 04:42:24 2012
Last write time: Tue Aug 7 04:39:19 2012
Mount count: 3
Maximum mount count: 37
Last checked: Tue Aug 7 04:37:37 2012
Check interval: 15552000 (6 months)
Next check after: Sun Feb 3 03:37:37 2013
Reserved blocks uid: 0 (user root)
Reserved blocks gid: 0 (group root)
First inode: 11
Inode size: 256 每个linode的大小
Journal inode: 8
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