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

[George Dunlap <George.Dunlap@xxxxxxxxxxxxx>]

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

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