SAS Link Reset, a down port, and I_T nexus loss

Gerry Houlder gerry.houlder at
Mon Apr 25 15:19:39 PDT 2011

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I think i can handle this one.
The Phy Disable signal is not like pulling the cable off the drive. Pulling
the cable will cause a Loss of Sync condition, then link reset (recovery
procedure), and eventually time out when the recovery fails too many times
(i.e., Nexus Loss).
Phy Disable signal is like a switch on the drive that disables the phy
without removing the cable. The drive detects this event immediately and
therefore disables the phy immediately.
On Mon, Apr 25, 2011 at 11:21 AM, <Edward.Younk at> wrote:
> * From the T10 Reflector (t10 at, posted by:
> * Edward.Younk at
> *
> Hi George,
> Ok, just one more question then. Why is this an immediate nexus loss,
> instead starting the I_T nexus loss timer?  It seems to me that this event
> should be handled in the same manner as the I_T nexus loss cases, i.e.
> start the I_T nexus loss timer.  As an example, a OPEN_REJECT(NO
> DESTINATION) starts the I_T nexus loss timer.  It could've been created by
> someone pulling the cable between the HBA and the expander up stream from
> my target. In this case we wait the I_T nexus loss timer before failing
> the initiator.  In addition, if the I_T nexus loss timer is set to 0xFFFF,
> i.e.( the timer is disabled) we wait forever for the nexus to return.  If
> someone pulls our target's cable however, it is an immediate nexus loss?
> Is this really what HBA's expect?

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