昨天看见rsync同步后用du -sh 显示的目录大小不同，感觉很困惑，以为同步出错，结果反复查也无果，今天来公司，上QQ群里问，最后确定是磁盘的block size 大小问题，经过 tune2fs -l /dev/sda1 命令查看，发现果然block size 一个是4096 一个是1024，故而确定 du 是文件所占用的磁盘空间大小，不是文件的实际大小；
block size 不一样，或者所占用的 blocks 数量不一样都会导致这种差异
[root@server02 down]# du --help
用法：du [选项]... [文件]...
总结每个<文件>的磁盘用量，目录则取总用量。
长选项必须用的参数在使用短选项时也是必须的。
-a, --all write counts for all files, not just directories
--apparent-size print apparent sizes, rather than disk usage; although
the apparent size is usually smaller, it may be
larger due to holes in (`sparse') files, internal
fragmentation, indirect blocks, and the like
-B, --block-size=SIZE use SIZE-byte blocks
-b, --bytes equivalent to `--apparent-size --block-size=1'
-c, --total produce a grand total
-D, --dereference-args dereference FILEs that are symbolic links
-H like --si, but also evokes a warning; will soon
change to be equivalent to --dereference-args (-D)
-h, --human-readable print sizes in human readable format (e.g., 1K 234M 2G)
--si like -h, but use powers of 1000 not 1024
-k like --block-size=1K
-l, --count-links count sizes many times if hard linked
-L, --dereference dereference all symbolic links
-P, --no-dereference don't follow any symbolic links (this is the default)
-0, --null end each output line with 0 byte rather than newline
-S, --separate-dirs do not include size of subdirectories
-s, --summarize display only a total for each argument
-x, --one-file-system skip directories on different filesystems
-X FILE, --exclude-from=FILE Exclude files that match any pattern in FILE.
--exclude=PATTERN Exclude files that match PATTERN.
--max-depth=N print the total for a directory (or file, with --all)
only if it is N or fewer levels below the command
line argument; --max-depth=0 is the same as
--summarize
--help 显示此帮助信息并离开
--version 显示版本信息并离开
SIZE may be (or may be an integer optionally followed by) one of following:
kB 1000, K 1024, MB 1000*1000, M 1024*1024, and so on for G, T, P, E, Z, Y.
http://gaizaoren.blog.51cto.com/622250/147728
