Abstract: Techniques for managing metadata storage units involve: in response to receiving, from a client, a request for allocating a target number of metadata storage units, determining a first number of available metadata storage units remaining in a metadata storage space of a storage system after the allocation is performed; and if the first number is not less than a reserved number, allocating the target number of metadata storage units from the metadata storage space for the client to use, wherein the reserved number is associated with a usage condition of the metadata storage units in the storage system. Accordingly, such techniques can effectively manage metadata and improve the performance of a system.

Abstract: Embodiments of the present disclosure relate to methods, devices and computer program products for writing data in a disk array in a storage system. The storage system comprises a disk array. The method comprises: in response to receiving a write request to write new data to a data block in at least one disk array group in a degraded mode within a disk array, reading old data stored in the data block and old parity information stored in a parity block associated with the data block. The method further comprises: determining new parity information associated with the new data based on the old data, the old parity information and the new data. The method further comprises: writing the new data and the new parity information into at least one cache page provided by a cache component in the storage system, the at least one cache page being allocated in a persistent memory in the cache component.

Abstract: Techniques provide for managing storage devices. Such techniques involve: combining storage devices in a redundant array of independent disks into a group of storage devices in an order of physical capacities of the storage devices; determining a first number of sets of storage devices based on a number of storage devices in the group and a threshold number of storage devices to be divided into each of the sets; and dividing, based on a configuration of the redundant array of independent disks, the group of storage devices into the first number of sets of storage devices, to optimize an effective capacity of the redundant array of independent disks.

Abstract: Techniques involve: writing, when a first disk for dirty page storage has a failure, a first target page description generated by a first node and associated with a first set of target dirty pages of the first node and a second set of target dirty pages of a second node to a first page description storage layer for the first node in a second disk; writing a second target page description generated by the second node and associated with the first set of target dirty pages and the second set of target dirty pages to a second page description storage layer for the second node in the second disk; and restoring, when the failure has been eliminated, the first set of target dirty pages and the second set of target dirty pages in the first disk based on at least one of the descriptions.

Abstract: The present disclosure relates to a method, a device, and a computer program product for managing a storage system. The storage system includes a first control node, a second control node, and a persistent storage device, the first control node being in an activated state, and the second control node being in a state of transfer from a non-activated state to an activated state. A method includes: loading a first list of page descriptors of the storage system to the second control node to generate a second list of page descriptors at the second control node, the first list including a portion of multiple page descriptors of the storage system that has been modified but has not been flushed to the persistent storage device; receiving a synchronization message from the first control node that indicates that the first list has been modified by the first control node; and updating the second list at the second control node based on the synchronization message.

Abstract: Techniques involve: writing, when a first disk for dirty page storage has a failure, a first target page description generated by a first node and associated with a first set of target dirty pages of the first node and a second set of target dirty pages of a second node to a first page description storage layer for the first node in a second disk; writing a second target page description generated by the second node and associated with the first set of target dirty pages and the second set of target dirty pages to a second page description storage layer for the second node in the second disk; and restoring, when the failure has been eliminated, the first set of target dirty pages and the second set of target dirty pages in the first disk based on at least one of the descriptions.

Abstract: Techniques for managing metadata storage units involve: in response to receiving, from a client, a request for allocating a target number of metadata storage units, determining a first number of available metadata storage units remaining in a metadata storage space of a storage system after the allocation is performed; and if the first number is not less than a reserved number, allocating the target number of metadata storage units from the metadata storage space for the client to use, wherein the reserved number is associated with a usage condition of the metadata storage units in the storage system. Accordingly, such techniques can effectively manage metadata and improve the performance of a system.

Abstract: The present disclosure relates to a method, a device, and a computer program product for managing a storage system. The storage system includes a first control node, a second control node, and a persistent storage device, the first control node being in an activated state, and the second control node being in a state of transfer from a non-activated state to an activated state. A method includes: loading a first list of page descriptors of the storage system to the second control node to generate a second list of page descriptors at the second control node, the first list including a portion of multiple page descriptors of the storage system that has been modified but has not been flushed to the persistent storage device; receiving a synchronization message from the first control node that indicates that the first list has been modified by the first control node; and updating the second list at the second control node based on the synchronization message.

Abstract: Embodiments of the present disclosure relate to a method and apparatus for managing cache. The method comprises determining a cache flush time period of the cache for a lower-layer storage device associated with the cache. The method further comprises: in response to a length of the cache flush time period being longer than a threshold length of time, in response to receiving a write request, determining whether data associated with the write request has been stored into the cache. The method further comprises: in response to a miss of the data in the cache, storing the write request and the data in the cache without returning a write completion message for the write request.

Abstract: Techniques read data. Such techniques involve: in response to receiving a read request from the user for data on a physical data block, determining whether there is data state information corresponding to the physical data block. The data state information may include a plurality of units for respectively indicating availability of data stored in a plurality of sub-blocks of the physical data block. Such techniques further involve: in response to determining that there is data state information, selecting a target sub-block from the plurality of sub-blocks of the physical storage block based on the data state information. Such techniques further involve: providing the user with data stored in the target sub-block. Such techniques are capable of determining the availability of data at a finer granularity.

Abstract: A method and device for managing a storage system comprising multiple storage devices in a first layer and at least one backup storage device in a second layer. In response to receiving a request for writing target data to the storage system, storing the target data to a first portion of storage devices among the multiple storage devices in the first layer; storing a first parity, determined on the basis of a first algorithm, of data in the first portion of storage devices to a second portion of storage devices among the multiple storage devices in the first layer; and storing a second parity, determined on the basis of a second algorithm, of data in the first portion of storage devices to a first backup storage device of the at least one backup storage device in the second layer.

Abstract: Techniques involve managing a storage space. In response to receiving an allocation request for allocating a storage space, a storage space size and a slice size are obtained. A first storage system and a second storage system are selected from multiple storage systems, the first storage system and the second storage system includes a first storage device group and a second storage device group respectively, and the first storage device group does not overlap the second storage device group. A first slice group and a second slice group is obtained from the first storage system and the second storage system respectively, on the basis of the size of the storage space and the size of the slice. A user storage system is built at least on the basis of the first slice group and the second slice group, so as to respond to the allocation request.

Abstract: Techniques manage a cache. Such techniques involve creating a primary cache by a cache management module in a storage system. Such techniques further involve: in response to the primary cache being created, sending a first request to a hardware management module to obtain first information about a first virtual disk. Such techniques further involve: in response to receiving the first information from the hardware management module, creating a secondary cache using the first virtual disk. Such techniques further involve: in response to an available capacity of the primary cache being below a predetermined threshold, flushing at least one cache page in the primary cache to the secondary cache. In certain techniques, it is possible to use spare extents in the disk array to create the secondary cache to increase a total capacity of the cache in the system, thereby improving the access performance of the system.

Abstract: A method of managing operation of a data storage system (DSS) is provided. The method includes (a) reserving space within a dedicated metadata storage region (DMSR); (b) in response to determining that accommodating a storage request requires use of the reserved space, entering a restricted write mode; (c) while operating in the restricted write mode, using the reserved space in a process that frees space within the DMSR outside the reserved space; and (d) exiting the restricted mode in response to freeing space within the DMSR outside the reserved space. An apparatus, system, and computer program product for performing a similar method are also provided.

Abstract: Techniques process and manage a storage unit access. In accordance with such a technique, a data access request which is from a host system and for a first storage unit in the first storage system is received, wherein the first storage unit is a secondary storage unit; and the data access request is forwarded to a second storage unit in a second storage system associated with the first storage unit via a redirection link from the first storage system to the second storage system, wherein the second storage unit is a primary storage unit. Through such techniques, the host system can be allowed to send a data access request for the secondary storage unit, so that the host system does not need to resend the data access request, thereby reducing delay and interruption caused by such requests.

Abstract: A technique involves: in response to receiving a first request for adjusting a first width of a disk array to a second width, obtaining, based on source identification information of a source stripe group in the disk array in the first request, source block identification information of a source block associated with the source stripe group. The technique further involves: determining destination identification information of a destination stripe group associated with the second width for storing data. The technique further involves: storing, based on the source identification information and the destination identification information, source data and metadata for the source data from the source block into a destination block of the destination stripe group, the metadata including node identification information for accessing nodes of the source block. The technique further involves: adjusting the node to access the destination block based on the node identification information.

Abstract: Techniques manage a redundant array of independent disks. Such techniques involve: obtaining information on a wear level associated with each of a plurality of disks; selecting, based on the information on the wear level, a group of disks from the plurality of disks, a difference between the wear levels of any two of the group of disks being below a predetermined threshold; and creating a RAID with extents from the selected group of disks. Such techniques can sufficiently utilize the wear level to balance the data storage distribution among redundant arrays of independent disks, thereby enabling efficient management of redundant arrays of independent disks.

Abstract: Embodiments of the present disclosure relate to methods and apparatuses for data copy. A method comprises receiving, from a client module in a first processing unit, a read request for reading data from a first storage region. The method further comprises, in response to determining from the read request that the data is to be copied, obtaining, from a cache, a first bitmap associated with the first storage region, the first bitmap indicating if the first storage region is filled with zero. The method further comprises, in response to determining from the first bitmap that the first storage region is filled with zero, sending, to the client module, an indication that the data is zero.

Abstract: A method of managing operation of a data storage system (DSS) is provided. The method includes (a) reserving space within a dedicated metadata storage region (DMSR); (b) in response to determining that accommodating a storage request requires use of the reserved space, entering a restricted write mode; (c) while operating in the restricted write mode, using the reserved space in a process that frees space within the DMSR outside the reserved space; and (d) exiting the restricted mode in response to freeing space within the DMSR outside the reserved space. An apparatus, system, and computer program product for performing a similar method are also provided.

Abstract: Embodiments include a method performed by a computing device. The method includes (a) receiving a plurality of access requests to access data of a multilayered storage system; (b) in response to determining that a first access request can be served from a top data layer, executing the first access request by accessing the top data layer; (c) in response to determining that a second access request cannot be served from the top data layer, determining whether a current concurrency number of the top data layer is less than a permitted concurrency number (PCN) of the top data layer; and (d) in response to determining that the current concurrency number of the top data layer is not less than the PCN, waiting until the current concurrency number of the top data layer is less than the PCN and then executing the second access request by accessing another data layer below the top layer.