Resolving SAS timing issues for long-distance SAS extender

Abstract

This invention extends the distance at which a SAS extender can function. The distance is increased a large amount over the traditional 10 meters. As a result timers will not go off before the response can make a trip back. This is accomplished by emulating as a SAS expander, using SAS AIP's (Arbitration In Progress), and using a lookup table to determine which SAS events must be responded to immediately and which ones to be passed on to the remote link.

1 . A system for resolving serial attached small computer module interface timing issues for long distance serial attached small computer module interface extender, said system comprising:
 a lookup table; and   a first serial attached small computer module interface extender;   wherein an initiator sends serial attached small computer module interface traffic, over a first serial attached small computer module interface link, to said first serial attached small computer module interface extender;   said first serial attached small computer module interface extender is connected to a second serial attached small computer module interface extender, through a fibre channel;   said first serial attached small computer module interface extender emulates a serial attached small computer module interface expander;   a report general command received from said first serial attached small computer module interface link is responded to;   wherein it is indicated that said first serial attached small computer module interface extender is the serial attached small computer module interface expander, by setting an externally configurable route table bit;   said first serial attached small computer module interface extender having said lookup table;   based on said lookup table, said first serial attached small computer module interface extender determines whether to immediately respond on said first serial attached small computer module interface link, to encapsulate and forward said serial attached small computer module interface traffic toward a serial attached small computer module interface target via said fibre channel, or to do both to immediately respond on said first serial attached small computer module interface link and to encapsulate and forward said serial attached small computer module interface traffic toward said serial attached small computer module interface target via said fibre channel;   based on said lookup table, for resolving the timing issues including a first serial attached small computer module interface timer expiring due to the long distance interconnection between the first and the second serial attached small computer module interface extender, when the first serial attached small computer module interface extender immediately responding on said first serial attached small computer module interface link and encapsulating and forwarding said serial attached small computer module interface traffic toward said serial attached small computer module interface target, said first serial attached small computer module interface extender monitors for a corresponding response, coming via said fibre link, and handles said corresponding response, based on said lookup table;   said first serial attached small computer module interface extender encapsulates said serial attached small computer module interface traffic within frames of said fibre channel;   said encapsulated said serial attached small computer module interface traffic is forwarded to said second serial attached small computer module interface extender;   said encapsulated said serial attached small computer module interface traffic is removed; and   said serial attached small computer module interface traffic is forwarded to said serial attached small computer module interface target, over a second serial attached small computer module interface link.