On Mon, Jun 20, 2011 at 6:37 AM, Fam Zheng <famc...@gmail.com> wrote: > Is there any difference between bdrv_getlength and > bdrv_get_allocated_file_size for bs-file? If not, I can simplify it by > reusing it in two raw devices.
Yes, the two functions are different: POSIX sparse files (files with holes) take up less space on disk than their file size. For example a 1 GB file where you've only written the last byte and never touched any other blocks will only take up one block - the rest will be unallocated. So bdrv_getlength() == 1 GB and bdrv_get_allocated_file_size() == 4 KB (or whatever the file system block size is). You can look at this using the stat(1) command and dd(1) to only write the last byte of a file. Stefan
