On Fri, Aug 22, 2014 at 05:22:33PM +0200, Kevin Wolf wrote: > It's still useful because it happens to reduce the overhead in most > implementations and it's a relatively quick operation, but the best way > I know of to actually _fully_ preallocate is still writing zeros. Which > of the two the user wants, is a decision that qemu can't make for them.
This is a difficult situation. Possibly the choice is between - efficiently make the file fully allocated, that works in the vast majority of cases, but don't go crazy (ie. fallocate) - really really try as hard as possible to make sure that future allocations will never fail (ie. write random non-zero data to the file) Note that neither of these is the preallocation=... option as specified in this patch. Rich. -- Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones Read my programming and virtualization blog: http://rwmj.wordpress.com virt-df lists disk usage of guests without needing to install any software inside the virtual machine. Supports Linux and Windows. http://people.redhat.com/~rjones/virt-df/
