Method and apparatus for dual porting a single port serial ATA disk drive
First Claim
1. An apparatus for providing a plurality of ports to a device using a point to point communications protocol, comprising:
- a first data port, wherein said first data port is adapted for interconnection to said device;
a second data port;
a first signal path, wherein said second data port may be selectively interconnected to said first data port by said first signal path;
a third data port; and
a second signal path, wherein said third data port may be selectively interconnected to said first data port by said second signal path, wherein data is passed over said first signal path in a first mode of operation, wherein data is passed over said second signal path in a second mode of operation, wherein a portion of said first signal path is also a portion of said second signal path, wherein said first mode of operation is entered in response to at least one of a command and data received at said second data port, and wherein at least one of a command and data is prevented from being passed over said second signal path until at least one of a command and data is received from said device at said first data port in reply to said at least one of a command and data received at said second data port.
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Abstract
A method and an apparatus for providing multiple ports to a single port device are provided. According to the present invention, single port devices that are incapable of communicating across a shared communication bus, and therefore require a point to point communication channel, may be interconnected to multiple hosts using a switch assembly. The switch assembly selectively establishes a communication path between a single host and a device. Additionally, the present invention provides a method and apparatus by which computer subsystems, such as RAID storage subsystems, may be implemented using inexpensive storage devices. Furthermore, the present invention provides a method and apparatus for providing a high reliability computer subsystem by configuring the subsystem such that no single active component failure will result in the failure of the entire subsystem.
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Citations
22 Claims
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1. An apparatus for providing a plurality of ports to a device using a point to point communications protocol, comprising:
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a first data port, wherein said first data port is adapted for interconnection to said device; a second data port; a first signal path, wherein said second data port may be selectively interconnected to said first data port by said first signal path; a third data port; and a second signal path, wherein said third data port may be selectively interconnected to said first data port by said second signal path, wherein data is passed over said first signal path in a first mode of operation, wherein data is passed over said second signal path in a second mode of operation, wherein a portion of said first signal path is also a portion of said second signal path, wherein said first mode of operation is entered in response to at least one of a command and data received at said second data port, and wherein at least one of a command and data is prevented from being passed over said second signal path until at least one of a command and data is received from said device at said first data port in reply to said at least one of a command and data received at said second data port. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 22)
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10. A data storage system, comprising:
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a first device controller; a second device controller; a plurality of data storage devices, wherein each of said data storage devices requires point to point connection; a plurality of switch assemblies, wherein each of said switch assemblies comprises at least first, second, and third data ports, wherein said switch assemblies operate to selectively interconnect said first port to one of said at least second and third ports, and wherein for each of said switch assemblies only one of said second and third ports is interconnected to a one of said data storage devices while a transfer of a command or data through said first port is pending; a backplane, comprising; interconnections to said at least second and said third ports of said switch assemblies; and an interconnection to said first device controller, an interconnection to said second device controller; a plurality of first backplane signal paths, wherein said first device controller may communicate with a second port of any of said switch assemblies; and a plurality of second backplane signal paths, wherein said second device controller may communicate with a third port of any of said switch assemblies. - View Dependent Claims (11, 12, 13)
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14. A method for providing point to point communications between a plurality of hosts and a device, comprising:
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establishing a first communication channel between said device and a first of said hosts in response to a communication received from said first host; passing at least one of a command and data between said device and said first host over said first communication channel; and establishing a second communication channel between said device and a second of said hosts in response to a communication received from said second host, wherein said device is incapable of operation on a shared bus, wherein said first and second communications channels are established by a switch assembly having a plurality of states, comprising; a first state, wherein communications between said device and said first host are enabled, wherein communications between said device and said second host are disabled, and wherein said first state is maintained at least until a communication is received by said switch from said device in reply to said communication from said first host; and a second state, wherein communication between said device and said second host are enabled, wherein communications between said device and said first host disabled, and wherein said second state is maintained at least until a communication is received from said device in reply to said communication from said second host. - View Dependent Claims (15, 16, 17, 18, 19, 20, 21)
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Specification