In a method disclosed for writing data, a device receives data, divides the data into one or more data fragments, obtains a first parity fragment based on the one or more data fragments and a second parity fragment of a written data fragment in a stripe distributed across a plurality of nodes, stores the one or more data fragments and the first parity fragment in the stripe.

Example redundant array of independent disks (RAID) storage systems and methods provide rebuild of logical data groups. Storage devices are configured as a storage array for storing logical data groups distributed among the storage devices. The logical data groups are written in a configuration of RAID stripes in the storage devices. A failed storage device may be rebuilt using the RAID stripes and completed rebuilds of logical blocks may be tracked during the device rebuild process. A logical group rebuild status may be determined by comparing the completed rebuilds of logical blocks to a logical group map. The logical group rebuild status for each logical data group may be provided as complete in response to all logical blocks in the logical data group having been rebuilt. In the event the array rebuild fails, the logical groups that did complete rebuild may be brought online as a partially completed rebuild to prevent the loss of the entire array.

In a method disclosed for writing data, a device receives data, divides the data into one or more data fragments, obtains a first parity fragment based on the one or more data fragments and a second parity fragment of a written data fragment in a stripe distributed across a plurality of nodes, stores the one or more data fragments and the first parity fragment in the stripe.

Example redundant array of independent disks (RAID) storage systems and methods provide rebuild of logical data groups. Storage devices are configured as a storage array for storing logical data groups distributed among the storage devices. The logical data groups are written in a configuration of RAID stripes in the storage devices. A failed storage device may be rebuilt using the RAID stripes and completed rebuilds of logical blocks may be tracked during the device rebuild process. A logical group rebuild status may be determined by comparing the completed rebuilds of logical blocks to a logical group map. The logical group rebuild status for each logical data group may be provided as complete in response to all logical blocks in the logical data group having been rebuilt. In the event the array rebuild fails, the logical groups that did complete rebuild may be brought online as a partially completed rebuild to prevent the loss of the entire array.

In a parity-based redundancy scheme, a log is maintained that contains a record of storage writes and associated redundancy backups. A mapping of allocation information indicative of free and allocated portions of storage is stored. An indication is received of a change to the free and allocated portions of storage. An update to the mapping of allocation information is determined, and the update to the mapping of allocation information is stored. The stored update is accessed and the redundancy backup is synchronized with stored data in response to a power interruption.

In a parity-based redundancy scheme, a log is maintained that contains a record of storage writes and associated redundancy backups. A mapping of allocation information indicative of free and allocated portions of storage is stored. An indication is received of a change to the free and allocated portions of storage. An update to the mapping of allocation information is determined, and the update to the mapping of allocation information is stored. The stored update is accessed and the redundancy backup is synchronized with stored data in response to a power interruption.

A method for execution by a dispersed storage and task (DST) execution unit includes obtaining a list slice request. At least one other storage unit affiliated with a DSN address range of the list slice request is identified and at least one proxied list slice request is issued to the at least one other storage unit. At least one received proxied list slice response associated with the list slice request is selected, and a list slice response is issued to the requesting entity based on the at least one selected proxied list slice response and locally stored encoded data slices associated with the list slice request.

A method for redundant array of independent disks (RAID) consistency initialization. The method allows fast RAID creation of the RAID subsystem and the RAID is capable of accepting I/O access after completion of the RAID creation. The method comprises the steps of: setting a RAID configuration, creating an initialization progress table (IPT) for storing the progress states of the initialization of the RAID, and writing the IPT and the RAID configuration into a non-volatile memory device. After that, the RAID can accept I/O access and meantime a consistency initialization can be performed according to the IPT. In one example, the consistency initialization comprises a consecutive initialization mechanism consecutively progressing in background mode and an induced consistency initialization mechanism induced by an I/O accessing to the RAID.

A method includes determining, by a computing device of a dispersed storage network (DSN), a data priority level for a data object. The method further includes determining, by the computing device, slice priority levels based on the data priority level. The method further includes encoding, by the computing device, the data object into sets of encoded data slices. While writing the sets of encoded data slices to storage units, the method further includes detecting, by a rebuilding module of the DSN, a slice error for an encoded data slice. When the data priority level is below a data priority threshold and the slice has the first slice priority level, the method further includes facilitating rebuilding of the slice. When the data priority level is below the data priority threshold and the slice has the second slice priority level, the method further includes foregoing rebuilding of the slice.

A method includes receiving data objects at substantially the same time for storage. The method further includes determining priority levels for the data objects. The method further includes establishing write thresholds for encoding the data objects based on the priority levels. The method further includes dispersed storage error encoding the data objects to produce pluralities of sets of encoded data slices. The method further includes executing write operations to store the pluralities of sets of encoded data slices in storage units in accordance with the write thresholds. During execution of the write operations, the method further includes identifying encoded data slices that were not properly stored and determining rebuild priorities for them. The method further includes rebuilding at least some of the encoded data slices based on the rebuild priorities.