Patent ID: 8135907

Claim:
A method for retrieving a logical block, comprising: receiving a request to read the logical block; obtaining metadata associated with the logical block, wherein the metadata comprises: a replication type used to store the logical block; physical block locations in a storage pool for each physical block associated with the logical block, wherein each physical block location specifies one of a plurality of storage devices in the storage pool; selecting a first set of physical block locations using a wear-level selection policy, wherein selecting the first set of physical locations comprises: identifying the first set of physical block locations using the metadata, wherein the physical blocks at the first set of physical block locations combine to form the logical block, determining a wear cost to read each of the physical blocks located at the first set of physical block locations to obtain a first plurality of wear costs, combining the first plurality of wear costs to obtain a first aggregate wear cost, identifying a second set of physical block locations using the metadata, wherein the physical blocks at the second set of physical block locations combine to form the logical block, determining a wear cost to read each of the physical blocks located at the second set of physical block locations to obtain a second plurality of wear costs, combining the second plurality of wear costs to obtain a second aggregate wear cost, and selecting the first set of physical block locations based on the first aggregate wear cost, the second aggregate wear cost, and the wear-level selection policy; generating a first set of I/O requests, wherein each I/O request specifies one of the first set of physical block locations; issuing a first set of I/O requests; receiving the first set of physical blocks in response to the first set of I/O requests; and constructing the logical block using the first set of physical blocks.