Apparatus and method for performing fast fibre channel write operations over relatively high latency networks
First Claim
1. An apparatus, comprising:
- a Switch, the Switch including;
a port configured to receive a write command defining an initiating Host and a target;
a trapping mechanism configured to trap the write frame if the write command designates a predetermined Host_ID and a predetermined target_ID; and
a processor configured to process trapped write commands by modifying either the OX_ID or RX_ID of the write command header.
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Abstract
A method and apparatus to improve the performance of a SCSI write over a high latency network. The apparatus includes a first Switch close to the initiator in a first SAN and a second Switch close to the target in a second SAN. In various embodiments, the two Switches are border switches connecting their respective SANs to a relatively high latency network between the two SANs. In addition, the initiator can be either directly connected or indirectly connected to the first Switch in the first SAN. The target can also be either directly or indirectly connected to the second Switch in the second SAN. During operation, the method includes the first Switch sending Transfer Ready (Xfr_rdy) frame(s) based on buffer availability to the initiating Host in response to a SCSI Write command from the Host directed to the target. The first and second Switches then coordinate with one another by sending Transfer Ready commands to each other independent of the target'"'"'s knowledge. The second switch buffers the data received from the Host until the target indicates it is ready to receive the data. Since the Switches send frames to the initiating Host independent of the target, the Switches manipulate the OX_ID and RX_ID fields in the Fibre Channel header of the various commands associated with the SCSI Write. The OX_ID and RX_ID fields are manipulated so as to trap the commands and so that the Switches can keep track of the various commands associated with the SCSI write.
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Citations
23 Claims
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1. An apparatus, comprising:
a Switch, the Switch including;
a port configured to receive a write command defining an initiating Host and a target;
a trapping mechanism configured to trap the write frame if the write command designates a predetermined Host_ID and a predetermined target_ID; and
a processor configured to process trapped write commands by modifying either the OX_ID or RX_ID of the write command header. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20)
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21. A method comprising:
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trap write commands specifying a predesignated Host ID corresponding to a Host and target ID corresponding to a target and including an OX_ID value and an un-initialized RX_ID value at a Switch;
configuring the Switch to forward the write command to the target;
configuring the Switch to initialize the RX_ID of the write command; and
configuring the Switch to generate a Transfer Ready command including the initialized RX_ID value to the Host as a proxy for the target. - View Dependent Claims (22, 23)
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Specification