Re: Kernel Summit Request for Discussion: The Future of Target mode and Cloud storage on Linux

[Vladislav Bolkhovitin <vst@vlnb.net>]

James Bottomley wrote:
> On Fri, 2008-08-22 at 23:00 +0400, Vladislav Bolkhovitin wrote:
>> James Bottomley wrote:
>>> On Thu, 2008-08-21 at 18:31 -0500, Mike Christie wrote:
>>>> I think James also said something about moving STGT in-kernel to get 
>>>> performance gains, but I do not think it means that we have to push 
>>>> exact code that sits in Tomo's git tree from usrspace into the kernel. 
>>>> If along the way we replace it with scst or Nick's code and we end up 
>>>> with a variant of scst or Nicks code that can still support userspace 
>>>> targets then I do not think any one is going to make long threads like 
>>>> these have resulted in :)
>>> I meant actually allowing performance critical pieces to work either
>>> in-user or in-kernel.  How, I'm not sure ... if we could use the same
>>> code for both, that would be brilliant ... if we have to have separate
>>> pieces, that will be OK.
>>>
>>> The error injection and transport debug people think it's important to
>>> have the state machine in user space for fast prototyping and debugging,
>>> so I'm not going to take this away from them.
>> Nobody has been asking you about that. Simply, there's no need in it.
> 
> I wasn't aware you were privy to my conversations ... however, I suggest
> that you must have missed it.
> 
> Quite a few people who want to work on transports don't have the budget
> for the hardware.  Emulators are things they use to get around this
> problem.  To them, therefore, it's a definite need.

Seems, there is a confusion and we are writing about different things. I 
mean backstorage device emulation in user space (this is what scst_user 
provides), but seems you mean the opposite side of SCSI commands 
processing in target: target transports, i.e. target drivers, in user 
space, which emulate some SCSI transport, correct?

>>>> Will this work for everyone?
>>> Sounds like a plan.  (However, it also sounds suspiciously like the last
>>> plan we had from the storage summit which didn't actually attract any
>>> implementers ...)
>> I at that time heard nothing about it. Nobody asked me, nobody let me 
>> know about it and nobody asked me to participate. Nothing about it was 
>> in linux-scsi. It was completely behind my back.
> 
> http://www.usenix.org/events/lsf08/
> 
> summaries page 6.
> 
> The invitation to participate was here:
> 
> http://marc.info/?t=119325401900042

I was aware about the event, although for obvious reasons wasn't able to 
participate. I meant not it, but the decision and the plan. Neither one 
of them was published in any public place, wasn't it?

> James
> 
> 
>