Abstract: In general, this disclosure relates to storage of logical blocks in a storage device. Aspects of this disclosure describe techniques to monitor the frequency of access of one or more logical blocks referenced by one or more logical block addresses. Based on the frequency of access, in non-limiting aspects of this disclosure, a controller may select one or more physical blocks of a common memory storage block. The storage device may store the logical blocks in the selected physical blocks.

Abstract: Method and apparatus for handling data in a data storage device. In accordance with some embodiments, a memory space with a plurality of garbage collection units (GCUs) that are each arranged into pages of memory that store user data identified by logical addresses (LAs) and each GCU has a metadata region that stores metadata that correlates the LAs with physical addresses (PAs). A header region in each page of memory stores a bitmask and a sequence map of the LAs in each page that are used by a log manager to creates a bitmask table stored in a first cache and a hierarchical log stored in a second cache. The bitmask table and hierarchical log are used to determine when the LAs stored in the selected GCU are stale, and update the bitmask for each page in the selected GCU after the stale data has been erased.

Abstract: A data structure is formed that references a garbage collection metric for each of a plurality of associated garbage collection units of a flash memory device. Each garbage collection metric is based on one or more device state characteristics of the associated garbage collection unit. In response to a threshold change in the one or more device state variables, a region of interest within the data structure is sorted based on the garbage collection metrics. One or more garbage collection units are selected for garbage collection operations from the sorted region of interest.

Abstract: Method and apparatus for managing metadata associated with a data storage array. In accordance with various embodiments, a group of user data blocks are stored to memory cells at a selected physical address of the array. A multi-tiered metadata scheme is used to generate metadata which describes the selected physical address of the user data blocks. The multi-tiered metadata scheme provides an upper tier metadata format adapted for groups of N user data blocks, and a lower tier metadata format adapted for groups of M user data blocks where M is less than N. The generated metadata is formatted in accordance with a selected one of the upper or lower tier metadata formats in relation to a total number of the user data blocks in the group.

Abstract: Method and apparatus for ensuring a most recent version of data is retrieved from a memory, such as a non-volatile flash memory array. In accordance with various embodiments, a controller is adapted to sequentially store different versions of an addressable data block having a selected logical address in different locations within a memory. The controller assigns a revision indication value to each said version, with at least two of said stored versions concurrently sharing the same revision indication value. In some embodiments, the revision indication value constitutes a repeating cyclical sequence count that is appended to each block, or logically combined with a code value and stored with each block. The total number of counts in the sequence is less than the total number of versions resident in the memory.

Abstract: A method and apparatus for rebuilding a data set. In accordance with some embodiments, a data storage device is coupled to a host. An error condition associated with a memory of the data storage device is detected. Data stored in a first portion of the memory unaffected by said error condition is transferred to the host. A communication signal is output to the host that indicates that data stored in a second portion of the memory affected by said error condition will not be transferred to the host. The host reconstructs the data stored in the second portion of the memory responsive to the communication signal.

Abstract: Representative locations of a non-volatile, solid-state memory of an apparatus store characterization data. An event during which elapsed time is not measured by the apparatus is determined. In response to the event, temporal degradation of the non-volatile, solid-state memory during the event is estimated based on electrical characteristics of the representative locations.

Abstract: Method and apparatus for maintaining data integrity in a data storage device. In accordance with some embodiments, a memory space has a plurality of garbage collection units (GCUs) each arranged to store user data identified by logical addresses. Each GCU has a metadata region that stores metadata that correlates the logical addresses LBAs with physical addresses and a header region that stores descriptor data that identifies LBAs stored in the associated GCU. A control circuit identifies an error in the metadata from the descriptor data of a selected GCU and rebuilds the metadata to indicate a storage location of a most current version of data associated with a selected logical address.

Abstract: A first data set is written to first memory units identified as having a higher data reliability and a second data set is written to second memory units identified as having a lower data reliability than the first memory units. In some cases, the second data set may include metadata or redundancy information that is useful to aid in reading and/or decoding the first data set. The act of writing the second data set increases the data reliability of the first data set. The second data set may be a null pattern, such as all erased bits.

Abstract: A data structure is formed that references a garbage collection metric for each of a plurality of associated garbage collection units of a flash memory device. Each garbage collection metric is based on one or more device state characteristics of the associated garbage collection unit. In response to a threshold change in the one or more device state variables, a region of interest within the data structure is sorted based on the garbage collection metrics. One or more garbage collection units are selected for garbage collection operations from the sorted region of interest.

Abstract: A method and a system is provided for increasing reliability of data stored in storage segments by increasing redundancy data and by permitting user data to fit around defective locations in the storage segment. User data is compressed and reserved for a portion of a storage segment having a data size corresponding to an uncompressed size of the user data. The compressed user data is written to the reserved portion of the storage segment and a pad byte pattern is written to any remaining portion of the reserved portion of the storage segment. The remaining portion of the reserved portion of the storage segment is designated as unused.

Abstract: Method and apparatus for ensuring a most recent version of data is retrieved from a memory, such as a non-volatile flash memory array. In accordance with various embodiments, a controller is adapted to sequentially store different versions of an addressable data block having a selected logical address in different locations within a memory. The controller assigns a revision indication value to each said version, with at least two of said stored versions concurrently sharing the same revision indication value. In some embodiments, the revision indication value constitutes a repeating cyclical sequence count that is appended to each block, or logically combined with a code value and stored with each block. The total number of counts in the sequence is less than the total number of versions resident in the memory.

Abstract: Method and apparatus for enhancing reliability and integrity of data stored in a non-volatile memory, such as in a solid-state drive (SSD) having an array of flash memory cells. In accordance with various embodiments, a controller is adapted to harden data stored in a first location of said memory in relation to a detected loss of retention characteristics of the first location. In some embodiments, the data are hardened by storing redundancy information associated with said data in a second location of said memory. The redundancy information can be a redundant set of the data or higher level error correct codes (ECC). The hardened data can be recovered to the host during a read operation by accessing the data stored in both the first and second locations.

Abstract: An example method includes providing at least two data storage areas in a memory, providing a first amount of over-provisioning for a first of the at least two data storage areas and a second amount of over-provisioning for a second of the at least two data storage areas, categorizing data based on a characteristic of the data, and storing the data in one of the at least two data storage areas based on the categorization.

Abstract: A data storage apparatus and associated method involving a memory with a plurality of storage elements defining an associated set of stored data, and memory control logic that, responsive to a request to store first data in a first storage element of the plurality of storage elements, computes without storing to any of the plurality of storage elements first redundancy data for the associated set of stored data inclusive of the first data.

Abstract: Method and apparatus for managing metadata associated with a data storage array. In accordance with various embodiments, a group of user data blocks are stored to memory cells at a selected physical address of the array. A multi-tiered metadata scheme is used to generate metadata which describes the selected physical address of the user data blocks. The multi-tiered metadata scheme provides an upper tier metadata format adapted for groups of N user data blocks, and a lower tier metadata format adapted for groups of M user data blocks where M is less than N. The generated metadata is formatted in accordance with a selected one of the upper or lower tier metadata formats in relation to a total number of the user data blocks in the group.

Abstract: Method and apparatus for handling data in a data storage device. In accordance with some embodiments, a memory space with a plurality of garbage collection units (GCUs) that are each arranged into pages of memory that store user data identified by logical addresses (LAs) and each GCU has a metadata region that stores metadata that correlates the LAs with physical addresses (PAs). A header region in each page of memory stores a bitmask and a sequence map of the LAs in each page that are used by a log manager to creates a bitmask table stored in a first cache and a hierarchical log stored in a second cache. The bitmask table and hierarchical log are used to determine when the LAs stored in the selected GCU are stale, and update the bitmask for each page in the selected GCU after the stale data has been erased.

Abstract: In general, this disclosure relates to storage of logical blocks in a storage device. Aspects of this disclosure describe techniques to monitor the frequency of access of one or more logical blocks referenced by one or more logical block addresses. Based on the frequency of access, in non-limiting aspects of this disclosure, a controller may select one or more physical blocks of a common memory storage block. The storage device may store the logical blocks in the selected physical blocks.

Abstract: In general, this disclosure relates to garbage collection in a storage device. Aspects of this disclosure describe techniques to identify one or more candidate memory storage blocks that should be recycled during garbage collection. The one or more candidate memory storage blocks may be identified based at least on monitored soft metrics of the candidate memory storage blocks. During garbage collection, the identified one or more candidate memory storage blocks may be recycled to free up storage space.

Abstract: Method and apparatus for maintaining data integrity in a data storage device. In accordance with some embodiments, a memory space has a plurality of garbage collection units (GCUs) each arranged to store user data identified by logical addresses. Each GCU has a metadata region that stores metadata that correlates the logical addresses LBAs with physical addresses and a header region that stores descriptor data that identifies LBAs stored in the associated GCU. A control circuit identifies an error in the metadata from the descriptor data of a selected GCU and rebuilds the metadata to indicate a storage location of a most current version of data associated with a selected logical address.