I have fint the way to change the extent size hint mkfs.xfs -r extsize=40960 /dev/sda1 but I should rebuild the disk, do you have a way more smooth? On Mon, May 30, 2016 at 4:48 PM, baotiao wrote: > how can I set the extent size hint to a file with command line? > I have google for a lot, but I can't find a answer > > ---------------------------------------- > > Github: https://github.com/baotiao > Blog: http://baotiao.github.io > Stackoverflow: http://stackoverflow.com/users/634415/baotiao > Linkedin: http://www.linkedin.com/profile/view?id=145231990 > > On May 30, 2016, at 13:04, Dave Chinner wrote: > > On Mon, May 30, 2016 at 12:45:07PM +0800, baotiao wrote: > > This machine is running for qemu, the file is qemu qcow file type > > [root@w-openstack20 > /data/nova/instances/7898b630-c4ef-49ab-9ce9-3735e090c282]# file disk > disk: QEMU QCOW Image (v3), has backing file (path > /data/nova/instances/_base/3f27393376152ac352b2d85703011e38517e), > 429496729600 bytes > > > Oh, you're using delta/snapshot based qcow images. That, by it's > very nature, generates fragmented image files as they are a delta > over the backing file. > > .... > > actual 48421430, ideal 20716, fragmentation factor 99.96% > > How can I solve this problem, what do you suggest me to do? > > > Use a extent size hint (say 1-8MB) for your qcow2 image files so that > they don't fragment badly as they are written to. > > Cheers, > > Dave. > -- > Dave Chinner > david@fromorbit.com > > > -- --- Blog: http://www.chenzongzhi.info Twitter: https://twitter.com/baotiao Git: https://github.com/baotiao