Abstract: A method for data distribution, including distributing logical addresses among an initial set of devices so as provide balanced access, and transferring the data to the devices in accordance with the logical addresses. If a device is added to the initial set, forming an extended set, the logical addresses are redistributed among the extended set so as to cause some logical addresses to be transferred from the devices in the initial set to the additional device. There is substantially no transfer of the logical addresses among the initial set. If a surplus device is removed from the initial set, forming a depleted set, the logical addresses of the surplus device are redistributed among the depleted set. There is substantially no transfer of the logical addresses among the depleted set. In both cases the balanced access is maintained.

Abstract: A method for data distribution, including distributing logical addresses among an initial set of devices so as provide balanced access, and transferring the data to the devices in accordance with the logical addresses. If a device is added to the initial set, forming an extended set, the logical addresses are redistributed among the extended set so as to cause some logical addresses to be transferred from the devices in the initial set to the additional device. There is substantially no transfer of the logical addresses among the initial set. If a surplus device is removed from the initial set, forming a depleted set, the logical addresses of the surplus device are redistributed among the depleted set. There is substantially no transfer of the logical addresses among the depleted set. In both cases the balanced access is maintained.

Abstract: Some embodiments of the invention relate to an apparatus and a method of managing a snapshot storage pool (SSP) associated with a storage unit of a distributed data storage system. According to some embodiments of the invention, the apparatus may include a logic module and a controller. The logic module may be adapted to provide a threshold corresponding to a ratio between a current amount of storage resources used for storing snapshots in the SSP and a total storage capacity defined for the SSP. The controller may be adapted to trigger an action which may be effective for managing the SSP in response to the amount of storage resources used for storing snapshots in the SSP crossing the threshold.

Abstract: A method for operating a storage system, including storing data redundantly in the system and measuring respective queue lengths of input/output requests to operational elements of the system. The queue lengths are compared to an average queue length to determine respective performances of the operational elements of the storage system. In response to the average queue lengths and a permitted deviation from the average an under-performing operational element among the operational elements is identified. An indication of the under-performing operational element is provided to host interfaces in the storage system. One of the host interfaces receives requests for specified items of the data directed to the under-performing element, and in response to the indication, some of the requests are diverted from the under-performing operational element to one or more other operational elements of the storage system that are configured to provide the specified items of the data.

Abstract: A method for operating a storage system, including storing data redundantly in the system and measuring respective queue lengths of input/output requests to operational elements of the system. The queue lengths are compared to an average queue length to determine respective performances of the operational elements of the storage system. In response to the average queue lengths and a permitted deviation from the average an under-performing operational element among the operational elements is identified. An indication of the under-performing operational element is provided to host interfaces in the storage system. One of the host interfaces receives requests for specified items of the data directed to the under-performing element, and in response to the indication, some of the requests are diverted from the under-performing operational element to one or more other operational elements of the storage system that are configured to provide the specified items of the data.

Abstract: A method is disclosed for operating a data storage system having one or more network interfaces and a plurality of data storage nodes configured to provide redundant storage locations. The method includes storing a set of node partitions on a given storage node of the plurality of data storage nodes. The method also includes, following a recovery by the given storage node from a malfunction, making a determination for a node partition in the set whether the node partition is current or noncurrent, and processing the node partition according to the determination.

Abstract: A method for operating a storage system, consisting of performing an allocation of respective partitions of a physical storage resource of the storage system to respective hosts of the storage system. The method also includes changing the allocation while permitting the respective hosts of the storage system to access the physical storage resource.

Abstract: A method for operating a storage system, including storing data redundantly in the system and measuring respective queue lengths of input/output requests to operational elements of the system. The queue lengths are compared to an average queue length to determine respective performances of the operational elements of the storage system. In response to the average queue lengths and a permitted deviation from the average an under-performing operational element among the operational elements is identified. An indication of the under-performing operational element is provided to host interfaces in the storage system. One of the host interfaces receives requests for specified items of the data directed to the under-performing element, and in response to the indication, some of the requests are diverted from the under-performing operational element to one or more other operational elements of the storage system that are configured to provide the specified items of the data.

Abstract: A method for data distribution, including distributing logical addresses among an initial set of devices so as provide balanced access, and transferring the data to the devices in accordance with the logical addresses. If a device is added to the initial set, forming an extended set, the logical addresses are redistributed among the extended set so as to cause some logical addresses to be transferred from the devices in the initial set to the additional device. There is substantially no transfer of the logical addresses among the initial set. If a surplus device is removed from the initial set, forming a depleted set, the logical addresses of the surplus device are redistributed among the depleted set. There is substantially no transfer of the logical addresses among the depleted set. In both cases the balanced access is maintained.

Abstract: A method for storing data blocks, including forming the data blocks into groups comprising N·M data blocks, where N and M are different positive integers. For every group, the N·M data blocks are assigned to correspond to elements of an array comprising N rows and M columns. A respective parity block is calculated for each of the N rows and M columns, to form (N+M) parity blocks. The resulting (N+M) parity blocks and N·M data blocks are stored in respective storage devices.

Abstract: A method is disclosed for operating a data storage system having one or more network interfaces and a plurality of data storage nodes configured to provide redundant storage locations. The method includes storing a set of node partitions on a given storage node of the plurality of data storage nodes. The method also includes, following a recovery by the given storage node from a malfunction, making a determination for a node partition in the set whether the node partition is current or noncurrent, and processing the node partition according to the determination.

Abstract: A method for data distribution, including distributing logical addresses among an initial set of devices so as provide balanced access, and transferring the data to the devices in accordance with the logical addresses. If a device is added to the initial set, forming an extended set, the logical addresses are redistributed among the extended set so as to cause some logical addresses to be transferred from the devices in the initial set to the additional device. There is substantially no transfer of the logical addresses among the initial set. If a surplus device is removed from the initial set, forming a depleted set, the logical addresses oldie surplus device are redistributed among the depleted set. There is substantially no transfer of the logical addresses among the depleted set. In both cases the balanced access is maintained.

Abstract: A method is disclosed for operating a data storage system having one or more network interfaces and a plurality of data storage nodes configured to provide redundant storage locations. The method includes storing a set of node partitions on a given storage node of the plurality of data storage nodes. The method also includes, following a recovery by the given storage node from a malfunction, making a determination for a node partition in the set whether the node partition is current or noncurrent, and processing the node partition according to the determination.

Abstract: Upon receiving a request for one or a set of data blocks associated with a given data segment, a disk cache controller may retrieve into cache the some part of the entire data segment from a disk. Each data segment on a disk may include a fixed number of data blocks, and all data segments may include the same number of data blocks. Data segments may be dynamically defined and their locations and sizes may vary from segment to segment. Data segments may be defined when data is written to the disk, or may be defined at a later point. A table associated with a cache controller may store information as to the physical location or address on a disk of the starting point and/or size of each data segment.

Abstract: A system, method and circuit for efficiently managing a cache storage device. A cache storage device may include a cache management module. The cache management module may be adapted to generate a management unit and to associate the management unit with new data that is to be written into the cache. The cache management module may be further adapted to assign two or more allocation units for each management unit, to store the new data in the cache. A cache management module may include a management unit module. The management unit module may be adapted to generate management units associated with predefined global cache management functions. The cache management module may further include an allocation unit module in communication with the management unit module. The allocation unit module may be adapted to assign allocation units for storing data written into the cache.

Abstract: A storage system, consisting of one or more data storage logical units (LUs) formed in physical media. The LUs are adapted to receive command and respond to the commands to store and recall data. The storage system further includes a plurality of ports, each port being adapted to maintain a respective LU command queue for each of the LUs, such that upon receiving a command directed to one of the LUs, the port places the received command in the respective LU command queue. The port converts the received command to one or more converted commands at least some of which are directed to the physical media of the one of the LUs. The port then conveys the commands directed to the physical media in an order determined by the respective LU command queue.

Abstract: A method for creating logical volume snapshots in a data storage system, including receiving a first write command to write first data to a partition of a logical volume, generating a first partition descriptor record (PDR), and storing the first data at a first physical location associated with the first PDR. A snapshot command is then received to form a snapshot of the logical volume, after which a second write command is received to write second data to the partition. In response to the second write command, a second PDR is generated and the second data is stored at a second physical location associated with the second PDR. A pointer between the first PDR and the second PDR is generated. In response to a read command indicating a number of a desired snapshot of the logical volume, the first PDR is accessed using the pointer.

Abstract: A method for operating a data storage system that includes a plurality of mass storage devices, which are configured to store data redundantly, the method including determining a characteristic service level of one or more of the mass storage devices and defining a reduced service level, which is less than the characteristic service level. The method further includes performing the following steps automatically: detecting the reduced service level on a first mass storage device in the data storage system; determining that data on the first mass storage device is stored redundantly on a second mass storage device in the data storage system; and in response to detecting the reduced service level, diverting an input/output (IO) request for the data directed to the first mass storage device to the second mass storage device, while operating the first mass storage device at the reduced service level.

Abstract: A method for managing a data storage system, consisting of configuring a first cache to retrieve data from and store data at a first range of logical addresses (LAs) in a storage device. A second cache is configured to operate like the first cache. The method further includes configuring one or more third caches to retrieve data from and store data at a second range of LAs in the storage device. The method includes detecting an inability of the second cache to retrieve data from or store data at the first range of LAs. In response to the inability, at least one of the first cache and the one or more third caches are reconfigured to retrieve data from and store at the first range of LAs while continuing to retrieve data from and store at the second range of LAs.

Abstract: In accordance with some embodiments of the present invention, there is provided a cache management module for managing a cache memory device, comprising a groups management module adapted to define groups of allocation units in accordance with at least an operative criterion and to create a new group of allocation units whenever it is determined that in accordance with at least the operative criterion none of the one or more existing groups is appropriate to include an allocation unit, and a replacement procedure module adapted to manage the cache in terms of groups of allocation units, rather than in terms of discrete allocation units.