On Mon, Jan 3, 2011 at 6:11 AM, Ted Ts'o <tytso@xxxxxxx> wrote: > On Sun, Jan 02, 2011 at 08:35:39PM -0700, Andreas Dilger wrote: >> It was written that way because HPC applications writing to a shared >> file normally write to an offset of task_num * task_data_size so >> they do not overlap, and end up with a dense file. Similarly, >> bittorrent and parallel FTP clients will write dense files after >> seeking randomly around the file, and database files often end up >> dense as well. >> >> I'd rather fix the relatively few applications that expect >> permanently sparse files to use fadvise() to notify the kernel of >> this. > > Agreed, and I'm not sure there are enough applications that expect > permanently sparse files that's worth adding a new fadvise(). But if > we do add a new fadvise(), the default should clearly be the current > behavior. > > If someone knows of use cases where permanently sparse files are > common, please let us know! > Well, there's e2image of course, but using the qcow2 format is a better solution than fadvise in this case. Also, I believe that if one chooses to use VM with raw image format, it is mostly for the purpose or read performance, which implies that the image was fallocate'd. Am I wrong about this? Amir. -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
