Re: [Qemu-block] [Qemu-devel] Persistent bitmaps for non-qcow2 formats

[Kevin Wolf]

Am 28.08.2017 um 04:57 hat Fam Zheng geschrieben:
> On Fri, 08/25 15:44, Max Reitz wrote:
> > Well, OK.  The main argument against supporting anything but qcow2 is
> > "if you want features, use qcow2; and we are working on making qcow2 as
> > fast as possible."  I think that's a very good argument still.  At some
> > point I (and probably others, too) had the idea of making qcow2 files in
> > raw layout: 
> 
> Yes! I think this idea makes a whole lot of sense, too. Metadata tables can be
> generated so old implementation can still use it.

Maybe a nice way to attack this would be "huge pages", i.e. have a L1
entry flag that tells "this points directly to a huge cluster instead of
an L2 table". Gives us 512 MB clusters with a 64k cluster size, or a
maximum of 512 GB clusters with a 2 MB cluster size.

Huge clusters would only be used by qemu-img create if the respective
option is given, and only with preallocation.

Kevin