Embodiments of the present disclosure provide a method and device for RAID rebuilding. In some embodiments, there is provided a computer-implemented method. The method comprises: determining a spare redundant array of independent disks (RAID) group with spare capacity from a plurality of disks included in at least one RAID group of a storage pool; building spare logic units from the spare RAID group; and in response to a RAID group of the at least one RAID group of the storage pool being in a degradation state, rebuilding a failed disk in a degraded RAID group using the spare logic units.

A method for diagnosing memory, performed by a storage system, is provided. The method includes writing and reading through a communication channel to and from flash memory of each of a plurality of flash memory devices and a static random-access memory (SRAM) register of each of the plurality of flash memory devices. The method includes analyzing errors in read data from the reading through the communication channel, identifying types of errors among flash memory errors, SRAM register errors, and communication channel errors, based on the analyzing, and indicating at least one error and type of error from the read data.

A system and method for providing erasure code protection across multiple storage devices. A data switch in a storage system connects a plurality of storage devices to a remote host. Each storage device is also connected to a controller, e.g., a baseboard management controller. During normal operation, read and write commands from the remote host are sent to respective storage devices through the data switch. When a write command is executed, the storage device executing the command sends a copy of the data to the controller, which generates and stores erasure codes, e.g., on a storage device that is dedicated to the storage of erasure codes, and invisible to the remote host. When a device fails or is removed, the controller reconfigures the data switch to redirect all traffic addressed to the failed or absent storage device to the controller, and the controller responds to host commands in its stead.

Techniques involve determining whether data read from a redundant array of independent disks (RAID) is corrupted, the RAID including two parity disks. The techniques further involve determining, based on the read data being corrupted, whether single-disk data recovery can recover the corrupted data. The techniques further involve recovering, based on the single-disk data recovery failing to recover the corrupted data, the corrupted data using dual-disk data recovery. Such techniques may present a recovery solution for silent data corruption of a RAID with two parity disks, such that corrupted data can be recovered in the case of either a single-disk failure or a dual-disk failure, thereby improving the storage system performance.

Techniques for data processing involve: determining, from a disk array, a target disk used for data reconstruction of the disk array; and sending, to an indicating apparatus associated with the target disk, an indication that the target disk is used for the data reconstruction. In this way, such techniques can indicate to the user that the target disk is being used for data reconstruction to remind the user not to remove or move the target disk, thereby ensuring completion of the data reconstruction. Such a technique may improve data storage equipment operation by preventing user interference.

Techniques for disk failure control involve determining the number of failed disks in a Redundant Array of Independent Disks (RAID). The techniques further involve comparing the number of failed disks with a predetermined threshold; and in accordance with a determination that the number of failed disks exceeds the predetermined threshold, setting at least one non-failing disk in the RAID into a protection mode to prevent the at least one non-failing disk from being disconnected. Such techniques facilitate prevention of the user data loss in the RAID.

A method, computer program product, and computer system for identifying a bit for an allocation unit. It may be determined if data has been modified on the allocation unit while degraded. A rebuild of the allocation unit may be executed when the bit is a first value. The rebuild of the allocation unit may be skipped when the bit is a second value.

Techniques are directed to failure recovery of a storage system. In accordance with certain techniques, in response to detecting that a disk group of a memory system failed, failure duration of the disk group is recorded. If the failure duration does not reach a predetermined ready time limit and the disk group is in a degraded state, the disk group is maintained in a degraded but not ready state. The predetermined ready time limit is shorter than a logic unit number debounce time limit to avoid a data unavailable event. With such techniques, the possibility of occurrence of a data loss event may be reduced significantly while avoiding a data unavailable event.

A technique is directed to storing data on a plurality of storage devices of a data storage array. The technique involves, on each storage device of the plurality of storage devices, providing large disk extents and small disk extents for allocation to RAID extents. The technique further involves forming, from the large disk extents, a user-data RAID extent to store user data for the data storage array. The technique further involves forming, from the small disk extents, an internal-metadata RAID extent to store internal metadata for the data storage array. In some arrangements, spare space is reserved on one or more storage devices between large and small disk extents.

A technique is directed to storing data on a plurality of storage devices of a data storage array. The technique involves, on each storage device of the plurality of storage devices, providing large disk extents and small disk extents for allocation to RAID extents. The technique further involves forming, from the large disk extents, a user-data RAID extent to store user data for the data storage array. The technique further involves forming, from the small disk extents, an internal-metadata RAID extent to store internal metadata for the data storage array. In some arrangements, spare space is reserved on one or more storage devices between large and small disk extents.