Re: [gentoo-user] gentoo-sources and xen blktap driver?

[Michael Mol <mikemol@gmail.com>]

On Sat, Jan 7, 2012 at 11:35 AM, Pandu Poluan <pandu@poluan.info> wrote:
> On Jan 7, 2012 8:44 PM, "victor romanchuk" <rom@persimplex.net> wrote:
>>
>> Konstantinos Agouros wrote, at 01/07/2012 03:51 PM:
>> > since xen got into the mainstream kernel the way to go is to use
>> > gentoo-sources for dom0 and the domUs. However the blktap modules are
>> > not
>> > there. Is there any way to get this to work?
>>
>> blktap drivers were excluded from kernel mainline since 3.x, these two
>> threads
>> from xen-users mailing list might put some light in that context:
>>
>>
>> http://old-list-archives.xen.org/archives/html/xen-users/2011-07/msg00637.html
>>
>> http://old-list-archives.xen.org/archives/html/xen-users/2011-10/msg00065.html
>>
>> the latest sys-kernel/xen-sources containing working blktap (not blktap2)
>> is
>> 2.6.38 (this is buggy from my point of view; i'm still sitting on
>> 2.6.34-r5 for
>> production installations)
>>
>
> Can someone shed a light on the importance of blktap, i.e., why one would
> want to use it when -- as someone explained in the first email thread you
> gave -- blkfront+blkend is enough for paravirtualization?

Reading through the linked threads, it sounds like the benefit stems
from being able to shim things in between the front and back ends.

You might want that for any number of reasons:
* a block encryption layer
* a metering layer
* a read/write masking layer
* an intercept to have the block device exist on (or be mirrored to)
on another system.

etc.


-- 
:wq