Method and apparatus for grouping multiple sas expanders to form a single cohesive sas expander

Patent metadata

Field	Value
Publication number	US-2016188515-A1
Application number	US-201514846265-A
Country	US
Kind code	A1
Filing date	Sep 4, 2015
Priority date	Dec 30, 2014
Publication date	Jun 30, 2016
Grant date	—

Abstract

A SAS (Serial Attached SCSI or Serial Attached Small Computer System Interface) switch includes a master SAS expander and a multitude of slave expanders connected to the master SAS expander. Each slave expander has a distinct SAS address. The slave expanders are not directly connected to one another and communicate through the master expander. The SAS switch has a pair of SAS wide ports each having a multitude of SAS links each associated with one of the slave expanders. The slave expanders are configured to route SAS traffic in accordance with routing tables established by the master SAS expander. The master SAS expander is not directly connected to either of the SAS wide ports.

First claim

What is claimed is:

1 . A SAS (Serial Attached SCSI or Serial Attached Small Computer System Interface) switch, comprising:
a master SAS expander; a plurality of slave expanders connected to the master SAS expander, each of the plurality of slave expanders having a distinct SAS address and not being directly connected to other slave expanders; a first SAS wide port having a first plurality of SAS links each associated with a different one of the plurality of slave expanders; and a second SAS wide port having a second plurality of SAS links each associated with a different one of the plurality of slave expanders, wherein the plurality of slave expanders are configured to route SAS traffic in accordance with routing tables established by the master SAS expander, the master SAS expander not being directly connected to either the first or the second SAS wide ports.

2 . The SAS switch of claim 1 wherein the master SAS expander and the plurality of slave SAS expanders are configured to operate and respond as a single coherent SAS expander with a unified SAS address, wherein the first and the second wide ports are configured to connect to external SAS devices.

3 . The SAS switch of claim 1 wherein said master expander is configured to:
detect a failure with a first one of the plurality of SAS links; and
reroute a SAS traffic bound for the detected first one of the plurality of SAS links.

4 . The SAS switch of claim 1 wherein the each slave SAS expander is configured by the master SAS expander.

5 . The SAS switch of claim 4 wherein, in a SAS link identification sequence, the plurality of slave SAS expanders are configured to send IDENTIFY address frames which include the master SAS expander's SAS address and a plurality of PHY identifiers globally indexed within the SAS switch.

6 . The SAS switch of claim 1 wherein each of the first plurality of SAS links in the first SAS wide port and each of the second plurality of SAS links in the second SAS wide port is configured to have a distinct non-overlapping external PHY identifier.

7 . The SAS switch of claim 1 wherein each of the plurality of slave SAS expanders communicates with the master SAS expander using the slave expander's SAS address and a local PHY identifier.

8 . The SAS switch of claim 1 further comprising a third and a fourth wide ports, each link in each of the wide port is associated with a different one of the plurality of slave expanders, wherein the third SAS wide port is configured to connect the SAS switch to a third external SAS device, and the fourth SAS wide port is configured to connect the SAS switch to a fourth external SAS device.

9 . The SAS switch of claim 1 wherein each of the slave SAS expanders is configured to:
route SAS traffic among external SAS devices; and
route SAS management traffic to and from the master SAS expander.

10 . A method for forming a single coherent SAS (Serial Attached SCSI or Serial Attached Small Computer System Interface) expander, the method comprising:
assigning a SAS expander as a master SAS expander; assigning a plurality of SAS expanders as SAS slave expanders, the SAS master expander and each of the plurality of slave SAS expanders having distinct SAS addresses; connecting each of the slave SAS expanders to the master SAS expander through at least one internal SAS link; inhibiting direct connection between the plurality of slave SAS expanders; forming a first SAS wide port having a first plurality of SAS links each associated with a different one of the plurality of slave expanders; forming a second SAS wide port having a second plurality of SAS links each associated with a different one of the plurality of slave expanders, and configuring the plurality of slave expanders to route SAS traffic in accordance with routing tables established by the master SAS expander.

11 . The method of claim 10 further comprising:
configuring the slave SAS expanders such that the IDENTIFY address frames sent to external SAS devices by the slave expanders include a SAS ADDRESS field set to the master SAS expander's SAS address and a PHY IDENTIFIER field set to a PHY identifier that is uniquely indexed within the single coherent SAS expander.

12 . The method of claim 10 further comprising:
inhibiting direct connection between the master expander and the wide port.

13 . The method of claim 10 further comprising:
configuring the slave SAS expanders such that SAS traffic between two external SAS devices is routed via external SAS wide ports.

14 . The method of claim 10 wherein the master SAS expander is configured to:
detect a failure with a first one of a plurality of SAS links; and
reroute a SAS traffic bound for the first one of the plurality of SAS links.

15 . A method of managing an IDENTIFY address frame in a first SAS (Serial Attached Small Computer System Interface) device, wherein the first SAS device is characterized by a first set of values for the fields in the IDENTIFY address frame, the method comprising:
receiving a second set of values for the fields in the IDENTIFY address frame different from the first set of values; and sending an IDENTIFY address frame having the second set of values to another SAS device.

16 . The method of claim 15 further comprising:
receiving the second set of values for the fields in the IDENTIFY address from a first SAS link of the first SAS device; and
sending the second set of values for the fields in the IDENTIFY address to a second SAS link of the first SAS device.

17 . The method of claim 15 further comprising:
in a SAS switch having a master expander and a plurality of slave expander, configuring the routing table for each slave SAS expander such that, in a SAS link identification sequence, the plurality slave SAS devices is configured to send IDENTIFY address frames which include the master SAS expander's SAS address and a distinct external PHY identifier.

18 . In a single cohesive SAS (Serial Attached Small Computer System Interface) expander including a master SAS expander and a plurality of slave SAS expanders, a method for the master expander to create a fail-over SAS path, the method comprising:
receiving a PHY status change event from a slave SAS expander with a failed SAS link; performing a discovery process on the slave SAS expander reporting the failed SAS link and identifying the failed SAS link; performing discovery processes on other slave SAS expanders to find a replacement slave SAS expander that is capable of routing the SAS traffic affected by the failed SAS link; and configuring route entries to route affected SAS traffic to the replacement slave SAS expander.

19 . The method of claim 18 , wherein the slave SAS expander with the failed SAS link reports the PHY status change event to the master SAS expander via BROADCAST (Change) primitive.

20 . The method of claim 18 , wherein the failed SAS link is an external SAS link connected to an external SAS device.

Assignees

• Pmc Sierra Us Inc

Inventors

• Lin Jiashu

Classifications

• G06F13/362

  with centralised access control · CPC title

• G06F13/4282

  on a serial bus, e.g. I2C bus, SPI bus (on daisy chain buses G06F13/4247) · CPC title

• G06F13/4022 Primary

  using switching circuits, e.g. switching matrix, connection or expansion network (G06F13/4009 takes precedence) · CPC title