Method, system, and program for selecting a path to a device to use when sending data requests to the device
First Claim
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1. A method for selecting a path to a device to use when sending data requests to the device with respect to a storage medium accessed by the device, comprising:
- submitting data requests to the device on a first path;
maintaining device information indicating a position on the storage medium currently being accessed by a data transfer mechanism of the device that accesses the storage medium to execute the submitted data request;
selecting a second path to the device if the first path fails;
submitting data requests to the indicated position at the device on the selected second path;
sending a command to the device to determine a current position of the device if the position indicated in the device information is incorrect or unavailable; and
updating the position indicated in the device information with the current position returned in response to the command before submitting the data requests to the indicated position.
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Abstract
Provided are a method, system, and program for selecting a path to a device to use when sending data requests to the device. Data requests are submitted to the device on a first path. Device information is maintained indicating a position of a data transfer mechanism of the device that performs the submitted data request. A second path to the device is selected if the first path fails. Data requests are submitted to the indicated position at the device on the selected second path.
125 Citations
37 Claims
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1. A method for selecting a path to a device to use when sending data requests to the device with respect to a storage medium accessed by the device, comprising:
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submitting data requests to the device on a first path; maintaining device information indicating a position on the storage medium currently being accessed by a data transfer mechanism of the device that accesses the storage medium to execute the submitted data request; selecting a second path to the device if the first path fails; submitting data requests to the indicated position at the device on the selected second path; sending a command to the device to determine a current position of the device if the position indicated in the device information is incorrect or unavailable; and updating the position indicated in the device information with the current position returned in response to the command before submitting the data requests to the indicated position. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. A method for selecting a path to at least one device having a storage medium and a data transfer mechanism that access data in the storage medium, comprising:
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maintaining information indicating usage by applications of adapters to access the at least one device, wherein the adapters provide multiple paths to the at least one device; receiving a request from an application to access a target device comprising one of the at least one device; using the information indicating the usage of the adapters to select one path to the target device that utilizes one adapter having a lowest usage; and switching the path the application uses to access the target device to the selected path by updating a logical device address used to access the target device to indicate the selected path; assigning the updated logical device address to the application to use to submit multiple requests to the target device; maintaining device information indicating a position on the storage medium currently being accessed by the data transfer mechanism to execute the submitted request, wherein the application submits data requests to the indicated position at the updated logical device address assigned to the application; sending a command to the device to determine a current position of the device if the position indicated in the device information is incorrect or unavailable; and updating the position indicated in the device information with the current position returned in response to the command before submitting the data requests to the indicated position. - View Dependent Claims (14, 15)
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16. A system for selecting a path to a device to use when sending data requests to the device with respect to a storage medium accessed by the device, wherein the device includes a data transfer mechanism, comprising:
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means for submitting data requests to the device on a first path; means for maintaining device information indicating a position on the storage medium currently being accessed by the data transfer mechanism; means for selecting a second path to the device if the first path fails; means for submitting data requests to the indicated position at the device on the selected second path; means for sending a command to the device to determine a current position of the device if the position indicated in the device information is incorrect or unavailable; and means for updating the position indicated in the device information with the current position returned in response to the command before submitting the data requests to the indicated position. - View Dependent Claims (17, 18, 19, 20)
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21. A system for selecting a path to at least one device including a target device, a storage medium and a data transfer mechanism that accesses data in the storage medium, comprising:
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adapters; means for maintaining information indicating usage by applications of the adapters to access at least one device, wherein the adapters provide multiple paths to the at least one device; means for receiving a request from an application to access the target device; means for using the information indicating the usage of the adapters to select one path to the target device that utilizes one adapter having a lowest usage; and means for switching the path the application uses to access the target device to the selected path by updating a logical device address used to access the target device to indicate the selected path, wherein the updated logical device address is assigned to the application to use to submit multiple requests to the target device; means for maintaining device information indicating a position on the storage medium currently being accessed by the data transfer mechanism to execute the submitted request, wherein the application submits data requests to the indicated position at the updated logical device address assigned to the application; means for sending a command to the device to determine a current position of the device if the position indicated in the device information is incorrect or unavailable; and means for updating the position indicated in the device information with the current position returned in response to the command before submitting the data requests to the indicated position. - View Dependent Claims (22)
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23. A computer readable storage including executable code for selecting a path to a device to use when sending data requests to the device with respect to a storage medium accessed by the device, wherein the device includes a data transfer mechanism, wherein the executed code causes operations to be performed, the operations comprising:
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submitting data requests to the device on a first path; maintaining device information indicating a position on the storage medium currently being accessed by the data transfer mechanism; selecting a second path to the device if the first path fails; submitting data requests to the indicated position at the device on the selected second path; sending a command to the device to determine a current position of the device if the position indicated in the device information is incorrect or unavailable; and updating the position indicated in the device information with the current position returned in response to the command before submitting the data requests to the indicated position. - View Dependent Claims (24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34)
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35. A computer readable storage including executable code for selecting a path to at least one device having a storage medium and a data transfer mechanism that access data in the storage medium, wherein the code is executed to cause operations to be performed, the operations comprising:
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maintaining information indicating usage by applications of adapters to access the at least one device, wherein the adapters provide multiple paths to the at least one device; receiving a request from an application to access a target device comprising one of the at least one device; using the information indicating the usage of the adapters to select one path to the target device that utilizes one adapter having a lowest usage; switching the path the application uses to access the target device to the selected path by updating a logical device address used to access the target device to indicate the selected path, wherein the updated logical device address is assigned to the application to use to submit multiple requests to the target device; maintaining device information indicating a position on the storage medium currently being accessed by the data transfer mechanism to execute the submitted request, wherein the application submits data requests to the indicated position at the updated logical device address assigned to the application; sending a command to the device to determine a current position of the device if the position indicated in the device information is incorrect or unavailable; and updating the position indicated in the device information with the current position returned in response to the command before submitting the data requests to the indicated position. - View Dependent Claims (36, 37)
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Specification