Daniel P. Berrange wrote: > On Mon, Apr 27, 2009 at 02:10:10PM -0500, Eric Sandeen wrote: >> Now that we have ext4 as the new default filesystem, it'd be nice if we >> can get more applications to take advantage of some of the features. >> >> One big feature that has already been brought up on the list[1] is file >> preallocation, which allows an application to pre-allocate blocks it >> knows that it will eventually write into, thereby making sure it won't >> run out of space, and also generally getting a more efficient/contiguous >> file layout. >> >> * Come up with a list of apps which could benefit: > [snip] >> - virt image tools? > > We're one step ahead of you ! libvirt supports it as of 0.6.3 for its > raw file storage management APIs, and this is in Fedora 11 trees Cool! > http://git.et.redhat.com/?p=libvirt.git;a=commit;h=70e7672184ff639856d5f2f3bf7849464031dff9 > > Thanks to Amit Shah for doing the patch for us, and providing us some > compelling performance figures at the same time: > > http://www.amitshah.net/2009/03/comparison-of-file-systems-and-speeding.html Ah, that explains the call to posix_fallocate() I saw in the library :) Just FWIW, this will still be slow on ext3, but fast on ext4/xfs/btrfs/ocfs2 - as Amit's blog entry shows, I guess. If you didn't want to fall back to the slow behavior on ext3, you might consider only using fallocate() if it's there, rather than posix_fallocate(). But the behavior is up to you of course. :) -Eric -- fedora-devel-list mailing list fedora-devel-list@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/fedora-devel-list
