Re: [Xen-devel] [PATCH] libxl: prefer qdisk over blktap when choosing disk backend

[Fabio Fantoni <fabio.fantoni@xxxxxxx>]

Il 28/08/2013 12:59, George Dunlap ha scritto:
> On Wed, Aug 28, 2013 at 11:35 AM, Ian Jackson <Ian.Jackson@xxxxxxxxxxxxx> wrote:
> > Wei Liu writes ("Re: [PATCH] libxl: prefer qdisk over blktap when choosing disk 
> > backend"):
> > > On Tue, Aug 27, 2013 at 03:22:43PM +0100, Wei Liu wrote:
> > > > There are some disk formats commonly supported by both qdisk and blktap.
> > > > As qdisk is better supported and blktap is unmaintained, we choose qdisk
> > > > over blktap whenever possible.
> > The reason for this ordering was that most kernels nowdays don't have
> > blktap.  So you don't get blktap on new systems, only on old ones.
> > That's good for stability I think.
> >
> > Does that make any kind of sense ?
> I don't think the original reasoning makes sense.  On systems without
> blktap, the order of blktap / qdisk doesn't matter in the slightest.
> The order only matters on old systems, with blktap; and there it's
> better to use qdisk if possible, because it's maintained and blktap
> isn't.
>
>   -George
I think is good prefer qdisk also for significant performance increase 
in comparison with blktap2.
On attachment one benchmark about qdisk and blktap2 of previous month on 
windows 7 domU.
I used only qdisk on my test system for one month without found bugs for 
now.
Blktap is used only with xen, qdisk also with other softwares using 
qemu, is more supported/tested.
I think is better point to upstream software and/or software used also 
by other opensource project for have optimize the development / testing 
and then have a final solution as best quality, performance and reliability.
A good example are moved to upstream kernel and qemu (qemu still not 
enough in my opinion, I think that major of developer/users are wasting 
too much time on traditional while the upstream is now little used and 
tested unfortunately).
The only question that comes about this patch is about "the qemu 
traditional case", although I think it should be abandoned as soon as 
possible to point all to the upstream qemu.
Sorry for my bad english.

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