Seagate Technology Incorporated

The University of Tokyo

Chuo University

Shuhei Tanakamaru

Erich Franz Haratsch

Dana Lynn Simonson

Ken Takeuchi

Naveen Kumar

Scott McClure

Ryan James Goss

Improving performance in solid state devices (SSDs) by controlling or throttling the depth of the request queue. In one implementation, a method includes monitoring a request queue in a solid state device (an SSD), the request queue comprising a first request and a second request having an actual time interval therebetween, determining a number of active memory dies of the SSD, determining a target interval based on the number of active memory dies and a target number of active memory dies, and responsive to the actual time interval being less than the target interval, delaying acting on the second request until after the target interval.

Controlling SSD performance by the number of active memory dies

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.

Recovering from hard decoding errors by remapping log likelihood ratio values read from NAND memory cells

Improving performance in solid state devices (SSDs) by controlling or throttling the depth of the request queue. In one implementation, a method includes monitoring a request queue in a solid state device (an SSD), the request queue comprising a first request and a second request having an actual time interval therebetween, determining a queue depth for the request queue, determining a target interval based on the queue depth and a target queue depth, and responsive to the actual time interval being less than the target interval, delaying acting on the second request until after the target interval.

Controlling SSD performance by queue depth

A method includes determining a portion of a block of a storage device to read after programming, and reading the portion of the block and determining a maximum error count for the portion of the block. The maximum error count is compared to a threshold. When the maximum error count exceeds the threshold, a code rate of an error correction coding used to program the block is adjusted, or a code rate test is performed on the entire block.

Block health checking

A method includes programming data in a block of a storage device, and reading back the programmed data and determining a maximum error count for the block. A code rate index that satisfies correction of the maximum error count for the block is determined. A current code rate index is adjusted to the code rate index that satisfies correction of the maximum error count for the block.

Code rate adaptation

A semiconductor storage device includes at least one memory from among a primary memory, a mirror memory storing data corresponding to data stored in the primary memory, and a buffer memory; and a controller that controls the at least one memory so as to store data in the at least one memory and read data from the at least one memory.

Semiconductor storage device and control method for same

When detected number of errors data Nerror exceeds the upper limit number of errors Nmax, an error correction circuit of a memory controller stores twice as long data length as stored data length for execution Sdata as the data length for execution Sdata in a correction information memory unit, and code length Scref longer than the data length for execution Sdata and detectable more errors than the upper limit number of errors as the code length for execution Scode in the correction information memory unit(step Sand S). The error correction circuit encodes input data using BCH code having the stored code length for execution Scode, stored encoded data in a semiconductor memory device, is input data stored in the semiconductor memory device, performs error correction for input data using BCH code, and decode error corrected data.

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San Jose, CA, United States of America

Shuhei Tanakamaru