Reducing data copy operations for writing data from a network to storage of a cached data storage system by organizing cache blocks as linked lists of data fragments
First Claim
1. A storage system comprising a storage controller, a cache memory, and data storage, wherein the storage controller is programmed to respond to a request to access a specified logical block of data in the data storage by accessing a logical block index to determine whether or not the specified logical block of data is in the cache memory, and when the logical block index indicates that the specified logical block of data is in the cache memory, to access the specified logical block of data in the cache memory, and when the logical block index indicates that the specified logical block of data is not in the cache memory, to access the specified logical block of data in the data storage, wherein the cache memory contains a multiplicity of logical blocks of data, and each of the multiplicity of logical blocks of data contained in the cache memory is organized as a respective linked list of list elements containing fragments of the data of said each of the multiplicity of logical blocks of data contained in the cache memory.
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Abstract
In a network attached cached disk storage system, data is transmitted over the network in data packets having a data length that is much smaller than the logical block size for reading or writing to disk storage. To avoid copying of data from network port buffers to the cache memory, the cache blocks of the cache memory are organized as linked lists of list elements, which can be used as network port input or output buffers. For TCP data packets, for example, each list element has a data slot for storing up to 1,500 bytes, and a field indicating the number of bytes stored in the data slot.
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Citations
43 Claims
- 1. A storage system comprising a storage controller, a cache memory, and data storage, wherein the storage controller is programmed to respond to a request to access a specified logical block of data in the data storage by accessing a logical block index to determine whether or not the specified logical block of data is in the cache memory, and when the logical block index indicates that the specified logical block of data is in the cache memory, to access the specified logical block of data in the cache memory, and when the logical block index indicates that the specified logical block of data is not in the cache memory, to access the specified logical block of data in the data storage, wherein the cache memory contains a multiplicity of logical blocks of data, and each of the multiplicity of logical blocks of data contained in the cache memory is organized as a respective linked list of list elements containing fragments of the data of said each of the multiplicity of logical blocks of data contained in the cache memory.
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22. A storage system comprising a storage controller, a cache memory, and data storage, wherein the storage controller is programmed to respond to a request to access a specified logical block of data in the data storage by accessing a logical block index to determine whether or not the specified logical block of data is in the cache memory, and when the logical block index indicates that the specified logical block of data is in the cache memory, to access the specified logical block of data in the cache memory, and when the logical block index indicates that the specified logical block of data is not in the cache memory, to access the specified logical block of data in the data storage;
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wherein the cache memory contains a list element pool of list elements, and at least some of the list elements in the list element pool are linked in respective lists for a multiplicity of logical blocks of data;
wherein each list element in the list element pool includes a data slot, a field for a pointer to a next list element in the list element pool, and a field for an indication of how many bytes of data are contained in the data slot; and
wherein the storage controller has a network port for attachment to a data network for communicating data packets with clients in the data network, and the storage controller is programmed to use the list elements as transmit and receive buffers for communicating the data packets with the clients in the data network. - View Dependent Claims (23, 24, 25, 26, 27, 28, 29)
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30. A method of operating a storage system having a storage controller, a cache memory, and data storage for storing logical blocks of data, the storage controller having a network port for attaching the storage controller to a data network for communicating data packets with clients in the data network, the storage controller being programmed to respond to a request to access a specified logical block of data in the data storage by accessing a logical block index to determine whether or not the specified logical block of data is in the cache memory, and when the logical block index indicates that the specified logical block of data is in the cache memory, to access the specified logical block of data in the cache memory, and when the logical block index indicates that the specified logical block of data is not in the cache memory, to access the specified logical block of data in the data storage;
- wherein said method comprises;
said storage controller maintaining a pool of list elements in the cache memory, linking at least some of the list elements into respective linked lists for a multiplicity of the logical blocks of data stored in the data storage, and storing, in the list elements for each respective linked list for each of the multiplicity of the logical blocks of data stored in the data storage, the data of said each of the multiplicity of the logical blocks of data stored in the data storage; and
said storage controller using the list elements as transmit and receive buffers for communicating the data packets with the clients in the data network. - View Dependent Claims (31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43)
- wherein said method comprises;
Specification