On Thu, Dec 05, 2013 at 06:35:12PM +0800, Chunyan Liu wrote: > Btrfs has terrible performance when hosting VM images, even more when the guest > in those VM are also using btrfs as file system. One way to mitigate this bad > performance is to turn off COW attributes on VM files (since having copy on > write for this kind of data is not useful). > > According to 'chattr' manpage, NOCOW could be set to new or empty file only on > btrfs, so this patch tries to add a --nocow option to vol-create functions and > vol-clone function, so that users could have a chance to set NOCOW to a new > volume if that happens to create on a btrfs like file system. What effect / impact does setting this flag have from a functional POV ? Why would we not just unconditonally enable it on btrfs so it was fast "out of the box" ? I'm loathe to add a btrfs-specific flag to our public API. Daniel -- |: http://berrange.com -o- http://www.flickr.com/photos/dberrange/ :| |: http://libvirt.org -o- http://virt-manager.org :| |: http://autobuild.org -o- http://search.cpan.org/~danberr/ :| |: http://entangle-photo.org -o- http://live.gnome.org/gtk-vnc :| -- libvir-list mailing list libvir-list@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/libvir-list