Deadlock Scenario (?)

Elliott, Robert (Server Storage) elliott at
Thu Jun 24 07:18:45 PDT 2004

* From the T10 Reflector (t10 at, posted by:
* "Elliott, Robert (Server Storage)" <elliott at>
I think we should change the message used when "there are insufficient
routing resources" from Arbitrating (Waiting on Connection) to
Arbitrating (Waiting on Partial). 

In your example, the requests are not really waiting on a connection,
they are waiting on partial connections.  On the left, phys W and X are
returning Phy Status (Partial Pathway), not Phy Status (Connection), at
this time.  If there really were a narrow port on which the Phy Y
request was waiting, that would cause Arbitrating (Waiting on Partial).

Rob Elliott, elliott at
Hewlett-Packard Industry Standard Server Storage Advanced Technology

> -----Original Message-----
> From: owner-t10 at [mailto:owner-t10 at] On Behalf 
> Of Fred Dutton
> Sent: Wednesday, June 23, 2004 7:46 PM
> To: t10 at
> Subject: Deadlock Scenario (?)
> * From the T10 Reflector (t10 at, posted by:
> * Fred Dutton <fred.dutton at>
> *
> Assuming an edge expander supports a limited number of 
> connections (by limited I mean it only supports a number of 
> concurrent connections less than what is physically 
> possible). For example if an expander includes eight external 
> phys, then the maximum number of concurrent connections --end 
> device to end device-- is four but the SAS 
> specification only requires a minimum of one connection (see 
> 4.6.4). So the expander could, in theory, support a number of 
> connections less than four.
> Suppose two edge expanders supporting N connections each are 
> connected to each other forming a wide port with M physical 
> links, where M > N.
> Is it possible to get into a deadlock situation because there 
> are more links in the wide port than connections supported by 
> each expander?
> For discussion purposes, suppose two edge expanders that 
> support only one connection each, are connected to each other 
> through a wide X2 port.
> How should the following deadlock be resolved? (You may have 
> use mono space fonts to get this message to display correctly)
> ...
> Thanks,
> Fred Dutton
> ----------------------------------------------------
> Fred Dutton * QLogic * 949.389.6340
> *
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