Method and system for arbitrating priority bids sent over serial links to a multi-port storage device
View Patent ↗A system including a multi-port storage device (e.g., a disk drive) and at least two users, each user coupled to a port of the storage device by a serial link. The storage device has an operational portion and an interface (including arbitration circuitry) between its ports and the operational portion. In response to a set of competing priority bids from the users, the arbitration circuitry grants one bid (including by sending an acknowledgement to the successful bidder) and preferably holds each non-granted competing bid without sending any notification to the unsuccessful bidder until the successful bidder sends a deselect signal. The system can be a RAID system including at least two disk drives and at least two controllers, where at least one drive is a multi-port device shared by at least two of the controllers. Preferably, each priority bid and deselect signal is a primitive code (e.g., an ordered sequence of a 10-bit control character and three 10-bit data characters in SATA format). Other aspects of the invention are multi-port storage devices and users for use in such a system.
1. A system, including:
at least one multi-port storage device including ports, an operational portion, and a port interface coupled between the ports and the operational portion; and
at least two users, each of the users coupled to a different one of the ports by a serial link and configured to contend for access to the storage device by sending a priority bid to said one of the ports over the link, wherein the storage device is operable in a first mode to respond to a set of competing bids received at at least two of the ports from at least two of the users by granting one of the bids and causing a select acknowledgement to be sent over one said link to the user whose priority bid has been granted,
wherein the storage device is also operable in a second mode in which the port interface responds to signals received at a selected one of the ports but does not respond to any signal received at any of the other ports, and
wherein the storage device undergoes a transition from operation in the first mode to operation the second mode in response to a manual override signal and a port select signal, wherein the port select signal is indicative of said selected one of the ports.