Re: userspace block driver?

[Jeff Garzik <jgarzik@pobox.com>]

Jens Axboe wrote:
> On Wed, Nov 09 2005, Jeff Garzik wrote:
> 
>>Neil Brown wrote:
>>
>>>On Wednesday November 9, jgarzik@pobox.com wrote:
>>>
>>>
>>>>Has anybody put any thought towards how a userspace block driver
>>>>would work?
>>>
>>>
>>>Isn't this was enbd does? 
>>> http://www.it.uc3m.es/~ptb/nbd/
>>
>>Is there something there relevant for modern kernels?  I would sure hope 
>>I could come up with something more lightweight than that.
> 
> 
> I was going to say drbd, but then you did say more lightweight :-)
> 
> Is nbd completely screwed these days?

nbd does more than I want.

_All_ that is needed is flipping requests <somehow> to/from userspace. 
nbd messes directly with sockets and such, which I don't want.  It does 
way too much, hardcodes way too much.

loop is a closer model to a generic userspace block device than nbd, I 
think.

Though, answering your question directly, I do get the impression that 
in-kernel nbd has been left behind in favor of drbd and enbd, out in the 
few places where nbd-ish solutions are used.

	Jeff