[ofw] Dual port HCA's in target and initiator, both ports hooked up, don't enumerate each drive twice in WInOF SRP

[Chris Worley]

On Fri, Oct 15, 2010 at 6:12 PM, Fab Tillier <ftillier at microsoft.com> wrote:
<snip>
>>
>> Remove one link, and it continues to enumerate the drives; replace
>> that link and remove the other link and it continues to enumerate the
>> drives; does SRP have some sort of multipathing built-in when two
>> HCA's are connected back-to-back?  If so, what is the protocol for
>> using both ports (i.e. fail-over only, round-robin, etc...)?
>
> SRP keeps track of multiple paths over a single HCA, and hides them from the OS.  This dates to pre-built-in-MPIO support in Windows, and made it so that one would get rudimentary failover support.  The backup paths only get used when the active path fails.

This doesn't work :(

If I pull one of the cables, the other doesn't take over.  The running
benchmark just locks-up.
>
>>  If so,
>> how is it disabled (I want to use Windows built-in multipathing)?
>
> This would require code changes to the SRP driver, as well as to the bus driver to report an SRP device per local HCA port (rather than an SRP device per local HCA.)
>
<snip>
> This is "by design"...  Probably worth changing, or at least make it configurable so that those with MPIO can get the behavior they desire.

First, thanks for replying... I very much appreciate it.

Is there anyone who might be interested in some consulting (i.e. paid)
work on this?  If it worked, I'd say make it optional... but it
doesn't, so I say rip-out all the checks for the same node GUID's and
let MPIO handle it.

Thanks,

Chris