Method of rate snooping in a SAS/SATA environment
View Patent ↗A method and apparatus for determining a set of common link rates for communication between two storage network elements in a storage network system. During the speed negotiation process, a controlling storage network element receives supported link rate information from a connected storage network element without providing any information in return. By not providing such information, although the speed negotiation process may not be completed, the controlling storage network element is still able to determine the supported link rates of the connected storage network element.
1. A method of determining a set of common link rates for communication between a device having a set of supported link rates and a Serial Attached Small Computer System Interface or a Serial Advanced Technology Attachment (SAS/SATA) storage network element in a SAS/SATA storage network system, comprising:
a) transmitting an initial data stream to said SAS/SATA storage network element at one of said supported link rates;
b) receiving a reply data stream from said SAS/SATA storage network element at said one of said supported link rates;
c) reporting said one of said supported link rates as a common link rate if said reply data stream is received;
d) repeating steps b) to c) for each of said remaining supported link rates without said SAS/SATA storage network element entering an active state with said device;
e) determining a single link rate supported by all connected PHYs communicating in said SAS/SATA storage network system, the single link rate being one of said common link rates; and
f) restarting and performing speed negotiation to completion with one of said common link rates reported in step c).
2. The method of claim 1 wherein step d) includes repeating step a) for each of said remaining supported link rates.
3. The method of claim 1 wherein said SAS/SATA system is a Serial Attached Small Computer System Interface (SAS) system and wherein step a) comprises transmitting an ALIGN0 data stream.
4. The method of claim 1 wherein said SAS/SATA system is a SAS system wherein step b) comprises receiving an ALIGN1 data stream.
5. The method of claim 1 wherein said SAS/SATA system is a Serial Advanced Technology Attachment (SATA) Host system and wherein step a) comprises transmitting a D10.2 data stream pattern of Dwords or a D21.5 data stream pattern of Dwords.
6. The method of claim 1 wherein said SAS/SATA system is a SATA Host system wherein step a) comprises transmitting a COMWAKE signal.
7. The method of claim 1 wherein said SAS/SATA system is a SATA Host system wherein step b) comprises receiving an ALIGN0 data stream.
8. The method of claim 1 wherein said SAS/SATA system is a SATA Device system further comprising, prior to step a):
receiving an initiation signal from said storage network element.
9. The method of claim 8 wherein said step of receiving an initiation signal comprises receiving a COMWAKE signal.
10. The method of claim 1 wherein said SAS/SATA system is a SATA Device system wherein step a) comprises transmitting an ALIGN0 data stream.
11. The method of claim 1 wherein said SAS/SATA system is a SATA Device system wherein step b) comprises receiving an ALIGN0 data stream.
12. The method of claim 1 further comprising after step c):
storing said common link rate in a list of common link rates.
13. The method of claim 12 further comprising:
generating said list of common link rates.
14. Apparatus for determining a set of common link rates for communication between a device having a set of supported link rates and a Serial Attached Small Computer System Interface or a Serial Advanced Technology Attachment (SAS/SATA) storage network element in a SAS/SATA storage network system, said device comprising:
a controller having a transmitter and a receiver for communicating with said SAS/SATA storage network element, said transmitter for transmitting an initial data stream to said SAS/SATA storage network element at said supported link rates and said receiver for receiving a reply data stream from said SAS/SATA storage network element; and
a control unit for storing a list of common link rates;
wherein when said controller receives said reply data stream, said controller reports to said control unit to store a link rate at which said reply data stream was transmitted as a common link rate in said list of common link rates,
wherein said apparatus determines a single link rate supported by all connected PHYs communicating in said SAS/SATA storage network system, the single link rate being in said list of common link rates, and
wherein said controller restarts and performs speed negotiation to completion with said common link rate.
15. The apparatus of claim 14 wherein said SAS/SATA storage network system is a SAS system.
16. The apparatus of claim 14 wherein said SAS/SATA storage network system is a SATA system.
17. The apparatus of claim 16 wherein said SAS/SATA storage network element is selected from the group consisting of a SATA Host, a SATA Device, a SAS Initiator Device, a SAS Target Device, a SAS Host Controller and a SAS Expander.
18. The apparatus of claim 14 wherein said controller is a controlling PHY.
19. The apparatus of claim 18 wherein said controlling PHY is selected from the group consisting of a SATA Host PHY, a SATA Port Selector Device PHY, a SAS PHY performing SATA Host emulation, a SATA Device PHY, a SATA port selector host and a SAS PHY.
20. The apparatus of claim 14 wherein said control unit is a central processing unit (CPU).
21. A non-transitory computer readable storage medium containing computer instructions which, when executed, perform a method of determining a set of common link rates for communication between a device having a set of supported link rates and a Serial Attached Small Computer System Interface or a Serial Advanced Technology Attachment (SAS/SATA) storage network element in a SAS/SATA storage network system, comprising:
instructions for transmitting an initial data stream to said SAS/SATA storage network element at one of said supported link rates;
instructions for receiving a reply data stream from said SAS/SATA storage network element at said one of said supported link rates;
instructions for reporting said one of said supported link rates as a common link rate if said reply data stream is received;
instructions for repeating the steps for each of the remaining supported link rates without said SAS/SATA storage network element entering an active state with said device;
instructions for determining a single link rate supported by all connected PHYs communicating in said SAS/SATA storage network system, the single link rate being one of said common link rates, and
instructions for restarting and performing speed negotiation with one of said common link rates.
22. The method of claim 1 wherein step f) comprises restarting and performing speed negotiation to completion with a set of common link rates.
23. The method of claim 1 wherein step e) comprises determining a single link rate supported by three or more connected PHYs communicating in said SAS/SATA storage network system.
24. The method of claim 1 further comprising:
implementing, in all the connected PHYs, the single link rate determined to be supported by all the connected PHYs.
25. The apparatus of claim 14 wherein said controller restarts and performs speed negotiation to completion with a set of common link rates.
26. The apparatus of claim 14 wherein the apparatus determines the single link rate supported by three or more connected PHYs communicating in said SAS/SATA storage network system.
27. The apparatus of claim 14 wherein said apparatus implements, in all the connected PHYs, the single link rate determined to be supported by all the connected PHYs.
28. The non-transitory computer readable medium of claim 21 further comprising instructions for restarting and performing speed negotiation to completion with a set of common link rates.
29. The non-transitory computer readable medium of claim 21 further comprising instructions for determining a single link rate supported by three or more connected PHYs communicating in said SAS/SATA storage network system.
30. The non-transitory computer readable medium of claim 21 further comprising instructions for implementing, in all the connected PHYs, the single link rate determined to be supported by all the connected PHYs.