The present disclosure relates to methods and systems for implementing redundancy in memory controllers. The disclosed systems and methods utilize a row of memory blocks, such that each memory block in the row is associated with an independent media unit. Failures of the media units are not correlated, and therefore, a failure in one unit does not affect the data stored in the other units. Parity information associated with the data stored in the memory blocks is stored in a separate memory block. If the data in a single memory block has been corrupted, the data stored in the remaining memory blocks and the parity information is used to retrieve the corrupted data.

Systems and methods are described for providing rapid access to data objects stored in a cache. Rather than storing data objects directly, each object can be broken into a number of parts via erasure coding, which enables the object to be generated from less than all parts. When servicing a request for the data object, a device can attempt to retrieve all parts, but begin to generate the data object as soon as a sufficient number of parts is retrieved, even if requests for other parts are outstanding. In this way, the data object can be retrieved without delay due to the slowest requests. For example, where one or more requests timeout, such as due to failure of cache devices, this timeout may have no effect on time required to retrieve the data object from the cache.

Hard errors are determined for an unsuccessful decoding of codeword bits read from NAND memory cells via a read channel and input to a low-density parity check (LDPC) decoder. A bit error rate (BER) for the hard errors is estimated and BER for the read channel is estimated. Hard error regions are found using a single level cell (SLC) reading of the NAND memory cells. A log likelihood ratio (LLR) mapping of the codeword bits input to the LDPC decoder is changed based on the hard error regions, the hard error BER, and/or the read channel BER.

A memory subsystem has multiple memory devices coupled to a command/address line and an error alert line, the error alert line delay-compensated to provide deterministic alert signal timing. The command/address line and the error alert line are connected between the memory devices and a memory controller that manages the memory devices. The command/address line is driven by the memory controller, and the error alert line is driven by the memory devices.

According to one embodiment, a memory system includes a nonvolatile memory and a controller. The controller manages a plurality of namespaces for storing a plurality of kinds of data having different update frequencies. The controller encodes write data by using first coding for reducing wear of a memory cell to generate first encoded data, and generates second encoded data to be written to the nonvolatile memory by adding an error correction code to the first encoded data. The controller changes the ratio between the first encoded data and the error correction code based on the namespace to which the write data is to be written.

A first data item is programmed to a first set of logical units of a memory sub-system. The first set of logical units is associated with a first fault tolerant stripe. A second data item is programmed to a second set of logical units of a memory sub-system. The second set of logical units is associated with a second fault tolerant stripe. A first set of redundancy metadata corresponding to the first data item and a second set of redundancy metadata corresponding to the second data item is generated. A combined set of redundancy metadata is generated based on at least the first set of redundancy metadata and the second set of redundancy metadata. The combined set of redundancy metadata is stored at a specified memory device of the memory sub-system.

A system includes a processing device, operatively coupled with a memory device, to perform operations including receiving a media access operation command designating a first memory location, and determining whether a first media access operation command designating the first memory location and a second media access operation designating a second memory location are synchronized, after determining that the first and second media access operation commands are not synchronized, determining that the media access operation command is an error flow recovery (ERF) read command, in response to determining that the media access operation command is an ERF read command, determining whether a head command of the first queue is blocked from execution, and in response to determining that the head command is unblocked from execution, servicing the ERF read command from a media buffer maintaining previously written ERF data.

A plurality of storage nodes in a single chassis is provided. The plurality of storage nodes in the single chassis is configured to communicate together as a storage cluster. Each of the plurality of storage nodes includes nonvolatile solid-state memory for user data storage. The plurality of storage nodes is configured to distribute the user data and metadata associated with the user data throughout the plurality of storage nodes such that the plurality of storage nodes maintain the ability to read the user data, using erasure coding, despite a loss of two of the plurality of storage nodes. A plurality of compute nodes is included in the single chassis, each of the plurality of compute nodes is configured to communicate with the plurality of storage nodes. A method for accessing user data in a plurality of storage nodes having nonvolatile solid-state memory is also provided.

An indication is received from a storage device that an attempt to read a portion of data from a block of the storage device has failed. A command is transmitted to the storage device to perform a scan on data stored at the block comprising the portion of data to acquire failure information associated with a plurality of subsets of the data stored at the block. The failure information associated with the plurality of subsets of the data stored at the block is received from the storage device.

The present disclosure generally relates to methods of operating storage devices. The storage device comprises a controller comprising first random access memory (RAM1), second random access memory (RAM2), and a storage unit divided into a plurality of streams. When a write command is received to write data to a stream, change log data is generated and stored in the RAM1, the previous delta data for the stream is copied from the RAM2 to the RAM1 to be updated with the change log data, and the updated delta data is copied to the RAM2. The delta data stored in the RAM2 is copied to the storage unit periodically. The controller tracks which delta data has been copied to the RAM2 and to the storage unit. During a power failure, the delta data and the change log data are copied from the RAM1 or the RAM2 to the storage unit.