A distributed storage places data units and parity units constituting a stripe formed by divided data into storage nodes in a distributed manner. In reference to determination formulas, either a full-stripe parity calculation method or an RPM parity calculation method is selected so as to minimize an amount of network traffic.

A processing system of a storage network operates by: sending, to at least one storage unit of the storage network, at least one read request corresponding to at least a read threshold number of a set of encoded data slices to be retrieved, wherein the set of encoded data slices correspond to a data segment, wherein the data segment is coded in accordance with dispersed error coding parameters that include a write threshold number and the read threshold number, wherein the write threshold number is a number of encoded data slices in the set of encoded data slices and wherein the read threshold number is a number of the set of slices that is required to decode the data segment; receiving, via the at least one processing circuit and from the at least one storage unit, a first subset of encoded data slices of the set of encoded data slices, wherein the first subset of encoded data slices is missing at least one missing encoded data slice that was not received from the at least one storage unit in response to the at least one read request and wherein the number of encoded data slices in the first subset of the encoded data slices is less than the read threshold number; generating, via the at least one processing circuit, at least one rebuilt encoded data slice corresponding to the at least one missing encoded data slice utilizing locally decodable redundancy data, wherein the locally decodable redundancy data generated from a second subset of the set of encoded data slices that includes the at least one missing encoded data slice; and recovering, via the at least one processing circuit, the data segment based on the at least one rebuilt encoded data slice and the first subset of encoded data slices.

A method for execution by a computing device of a storage network begins or continues by generating a plurality of estimated efficiency models associated with a plurality of processing units of the storage network, where an estimated efficiency model of the plurality of estimated efficiency models includes estimated efficiency probabilities, and where the estimated efficiency probabilities correspond to data access request types for a processing unit of the plurality of processing units. The method further includes storing the plurality of estimated efficiency models in memory of the storage network.

A method includes, determining, for a batch rebuild process regarding a first batch threshold number of encoded data slices of a set of encoded data slices that need rebuilding, a target storage unit of target storage units of a set of storage units of the storage network is unavailable, where a data segment of data is dispersed storage error encoded into the set of encoded data slices, the set of encoded data slices is stored in the set of storage units, and the first batch threshold number of encoded data slices is to be stored in the target storage units. When the target storage unit becomes available before a second batch rebuild threshold number of encoded data slices of the set of encoded data slices is met, the method includes executing the batch rebuild process for the first batch threshold number of encoded data slices.

A distributed storage integrity system in a dispersed storage network includes a scanning agent and a control unit. The scanning agent identifies an encoded data slice that requires rebuilding, wherein the encoded data slice is one of a plurality of encoded data slices generated from a data segment using an error encoding dispersal function. The control unit retrieves at least a number T of encoded data slices needed to reconstruct the data segment based on the error encoding dispersal function. The control unit is operable to reconstruct the data segment from at least the number T of the encoded data slices and generate a rebuilt encoded data slice from the reconstructed data segment. The scanning agent is located in a storage unit and the control unit is located in the storage unit or in a storage integrity processing unit, a dispersed storage processing unit or a dispersed storage managing unit.

A processing system of a storage network operates by: sending, to at least one storage unit of the storage network, at least one read request corresponding to at least a read threshold number of a set of encoded data slices to be retrieved, wherein the set of encoded data slices correspond to data, wherein the data is coded in accordance with dispersed error coding parameters that include a write threshold number and the read threshold number, wherein the write threshold number is a number of encoded data slices in the set of encoded data slices and wherein the read threshold number is a number of the set of encoded data slices that is required to decode the data; receiving, via the at least one processing circuit and from the at least one storage unit, a first subset of the set of encoded data slices, wherein the first subset is missing at least one missing encoded data slice that was not received from the at least one storage unit in response to the at least one read request and wherein a number of encoded data slices in the first subset is less than the read threshold number; generating, via the at least one processing circuit, at least one rebuilt encoded data slice corresponding to the at least one missing encoded data slice utilizing locally decodable redundancy data, wherein the locally decodable redundancy data generated from a second subset of the set of encoded data slices that includes the at least one missing encoded data slice; and recovering, via the at least one processing circuit, the data based on the at least one rebuilt encoded data slice and the first subset.

A method for execution by a computing device of a storage network includes obtaining performance information for a storage device of a set of storage devices of the storage network, wherein data is error encoded into sets of encoded data slices that are stored in the storage devices. The method further includes obtaining additional performance information for each storage device of the storage devices, wherein the additional performance information is based on historical data. The method further includes comparing the performance information to the additional performance information to produce comparison performance information and identifying at least one component of the comparison performance information. The method further includes comparing the at least one component to a corresponding error threshold and outputting indication of a performance error for the storage device when at least one component of the comparison performance information is greater than an error threshold.

A method and device for selecting a Redundant Array of Independent Disks (RAID) level for mapped RAID. The method comprises determining, for a given RAID level, a desired ratio of rebuilding speed between the mapped RAID and non-mapped RAID based on the first number of disks in the non-mapped RAID and the second number of disks in the mapped RAID. The method also comprises determining an actual ratio of rebuilding speed between the mapped RAID and the non-mapped RAID based on the second number of disks in the mapped RAID. In addition, the method comprises selecting the given RAID level for the mapped. RAID in response to the actual ratio being above the desired ratio.

A method for execution by one or more computing devices of a storage network includes obtaining performance impact information regarding a data reconstruction operation associated with a computing device of the one or more computing devices, where the data reconstruction operation is regarding reconstructing data at a first reconstruction rate of a plurality of reconstruction rates, and where the performance impact information includes performance metrics of the storage network affected by the data reconstruction operation. The method further includes determining a second reconstruction rate of the plurality of reconstruction rates to utilize for the data reconstruction operation based on the performance impact information to achieve a first performance metric of the performance metrics. The method further includes executing the data reconstruction operation in accordance with the second reconstruction rate.

A method and computer device for storage and retrieval of a data object on a storage medium. The method includes steps of disassembling the data object into a predetermined number of redundant sub blocks, storing the redundant sub blocks on the storage medium, retrieving at least a predetermined multiple of a minimal spreading requirement of the redundant sub blocks from the storage medium, and assembling the data object from any combination of a particular number of the redundant sub blocks, the particular number corresponding to a predetermined multiple of a minimal spreading requirement. The computer device includes modules for performing the steps.