A tag memory and a cache system with automating tag comparison mechanism and a cache method thereof are provided. The tag memory in the cache system includes a memory cell array, sensing amplifiers and a tag comparison circuit. The memory cell array stores cache tags, and outputs row tags of the cache tags according to an index in a memory address. The sensing amplifiers perform signal amplifications on the row tags to serve as comparison tags. The tag comparison circuit performs parallel comparisons between a target tag in the memory address and the row tags. When one of the row tags matches the target tag, the tag comparison circuit outputs a location of the matched row tag to serve as a first column address. The first column address is a column address where the memory address corresponds to a first data memory in the cache system.

In one embodiment, a node coupled to solid state drives (SSDs) of a plurality of storage arrays executes a storage input/output (I/O) stack having a plurality of layers. The node includes a non-volatile random access memory (NVRAM). A first portion of the NVRAM is configured as a write-back cache to store write data associated with a write request and a second portion of the NVRAM is configured as one or more non-volatile logs (NVLogs) to record metadata associated with the write request. The write data is passed from the write-back cache over a first path of the storage I/O stack for storage on a first storage array and the metadata is passed from the one or more NVLogs over a second path of the storage I/O stack for storage on a second storage array, wherein the first path is different from the second path.

A method of replication in a distributed storage system, performed by the distributed storage system is provided. The method includes managing a first index for data or metadata in a first storage system, the first storage system having a first partitioning scheme. The method includes managing a second index for data or metadata in a second storage system, the second storage system having a second partitioning scheme. The method includes replicating the data or metadata from the first storage system to the second storage system, translating an identifier of the data or metadata from the first storage system, and mapping the replicated data or metadata into the second partitioning scheme, via the translating of the identifier of the data or metadata from the first storage system.

A storage device includes a nonvolatile memory device, a random access memory that includes a first region and a second region, and a controller that is configured to use the first region of the random access memory as a journal memory for a journal indicating modification of data of the second region, expose a user region of the nonvolatile memory device to an external host device as a first access region of a block unit, and expose the second region of the random access memory to the external host device as both a second access region of the block unit and a third access region of a byte unit.

A method of replication in a distributed storage system, performed by the distributed storage system is provided. The method includes managing a first index for data or metadata in a first storage system, the first storage system having a first partitioning scheme. The method includes managing a second index for data or metadata in a second storage system, the second storage system having a second partitioning scheme. The method includes replicating the data or metadata from the first storage system to the second storage system, translating an identifier of the data or metadata from the first storage system, and mapping the replicated data or metadata into the second partitioning scheme, via the translating of the identifier of the data or metadata from the first storage system.

Combined operational steps and device characteristics help preserve data against integrity threats. Data is divided into critical data and non-critical data, based on criteria such as customer requirements, workload criticality, or virtual machine criticality. Data may be generated in a compute node for storage in a storage node, for example. Critical data is stored in a battery-backed memory aperture at physical addresses where it will be flushed ahead of the non-critical data due to a flush order imposed by or on the battery-backed memory, e.g., a bottom-up NVDIMM flush order. Redundant copies of the data (especially non-critical data) may also be kept in case it does not get flushed in time. Battery-backed memory apertures are sized and located according to their battery's characteristics, and may be relocated or resized as conditions change. Flush defragging is performed to optimize use of the aperture, especially within the portion that holds critical data.

Combined operational steps and device characteristics help preserve data against integrity threats. Data is divided into critical data and non-critical data, based on criteria such as customer requirements, workload criticality, or virtual machine criticality. Data may be generated in a compute node for storage in a storage node, for example. Critical data is stored in a battery-backed memory aperture at physical addresses where it will be flushed ahead of the non-critical data due to a flush order imposed by or on the battery-backed memory, e.g., a bottom-up NVDIMM flush order. Redundant copies of the data (especially non-critical data) may also be kept in case it does not get flushed in time. Battery-backed memory apertures are sized and located according to their battery's characteristics, and may be relocated or resized as conditions change. Flush defragging is performed to optimize use of the aperture, especially within the portion that holds critical data.

A method of replication in a distributed storage system, performed by the distributed storage system is provided. The method includes managing a first index for data or metadata in a first storage system, the first storage system having a first partitioning scheme. The method includes managing a second index for data or metadata in a second storage system, the second storage system having a second partitioning scheme. The method includes replicating the data or metadata from the first storage system to the second storage system, translating an identifier of the data or metadata from the first storage system, and mapping the replicated data or metadata into the second partitioning scheme, via the translating of the identifier of the data or metadata from the first storage system.

A technique manages data in a flash memory drive which includes single-level cell (SLC) flash memory and multi-level cell (MLC) flash memory. The technique involves performing, within the flash memory drive, data placement operations on data which has been written to the flash memory drive. The technique further involves, based on the data placement operations, storing hot data in the SLC flash memory. The technique further involves, based on the data placement operations, storing cold data in the MLC flash memory, the hot data being accessed more frequently than the cold data. Such hot data and cold data can be distinguished based on access frequency.

A storage device includes a nonvolatile memory device, a random access memory that includes a first region and a second region, and a controller that is configured to use the first region of the random access memory as a journal memory for a journal indicating modification of data of the second region, expose a user region of the nonvolatile memory device to an external host device as a first access region of a block unit, and expose the second region of the random access memory to the external host device as both a second access region of the block unit and a third access region of a byte unit.