On 01/09/15 12:39, Sagi Grimberg wrote:
> On 1/8/2015 4:11 PM, Bart Van Assche wrote:
>> On 01/08/15 14:45, Sagi Grimberg wrote:
>>> Actually I started with that approach, but the independent connections
>>> under a single session (I-T-Nexus) violates the command ordering
>>> requirement. Plus, such a solution is specific to iSER...
>>
>> Which command ordering requirement are you referring to ? The Linux
>> storage stack does not guarantee that block layer or SCSI commands will
>> be processed in the same order as these commands have been submitted.
>
> I was referring to the iSCSI session requirement. I initially thought of
> an approach to maintain multiple iSER connections under a single session
> but pretty soon I realized that preserving commands ordering this way
> is not feasible. So independent iSER connections means independent
> iSCSI sessions (each with a single connection). This is indeed another
> choice, which we are clearly debating on...
>
> I'm just wandering if we are not trying to force-fit this model. How
> would this model look like? We will need to define another entity to
> track and maintain the sessions and to allocate the scsi_host. Will that
> be communicated to user-space? How will error recovery look like?

Hello Sagi,

As you probably remember scsi-mq support was added in the SRP initiator
by changing the 1:1 relationship between scsi_host and RDMA connection
into a 1:n relationship. I don't know how much work it would take to
implement a similar transformation in the SCSI initiator. Maybe we
should wait until Mike's workday starts such that Mike has a chance to
comment on this.

Bart.


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