Process and apparatus to reduce declared capacity of storage device by conditionally trimming

A storage device and capacity technology, which is applied in the field of storage systems and can solve problems such as device wear and tear

Active Publication Date: 2017-08-01
SANDISK TECH LLC
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

Eventually, the charge storage capability degrades to the point where it becomes impossible or impossible to recover the original data (e.g., an unrecoverable codeword is read from the flash device, compu

Method used

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  • Process and apparatus to reduce declared capacity of storage device by conditionally trimming
  • Process and apparatus to reduce declared capacity of storage device by conditionally trimming
  • Process and apparatus to reduce declared capacity of storage device by conditionally trimming

Examples

Experimental program
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Embodiment Construction

[0025] When a multi-level flash memory cell has reached its wear limit, it typically still has sufficient charge retention to store a reduced amount of charge. It is often the case that most erase and reprogram cycles can be performed on wear-limited multi-level flash cells with full recovery of stored data, provided that a reduced amount of charge is used and desired. For example, a flash memory device operating in 3 bits per cell mode (TLC) can typically perform 500 to 1500 erase and reprogram cycles before it is considered worn out. However, at that point in time, there will typically still be enough charge storage capacity to operate in single-bit-per-cell mode (SLC) for an additional 10,000 to 20,000 erases and reprograms before the SLC wear limit is reached cycle. Thus, the lifetime of a flash memory device can be extended if the flash memory device is allowed to store less data. Currently, storage systems have difficulty taking advantage of this expanded capability be...

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PUM

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Abstract

Systems, methods, and/or devices are used to reduce declared capacity of a non-volatile memory of a storage device in a storage system. In one aspect, the method includes, detecting an amelioration trigger, and in accordance with the detected amelioration trigger, performing an amelioration process to reduce declared capacity of the non-volatile memory of the storage device. The method includes obtaining a target capacity of the non-volatile memory of the storage device and a current utilization rate of the non-volatile memory of the storage device, wherein the target capacity is lower than a current capacity of the non-volatile memory of the storage device and the current utilization corresponds to allocated logical addresses in a logical address space; in accordance with a determination that the target capacity is not greater than the current utilization, trimming at least a portion of the allocated logical addresses; and reducing declared capacity of the non-volatile memory of the storage device.

Description

technical field [0001] The disclosed embodiments relate generally to memory systems, and in particular to reducing the declared capacity of storage devices (eg, including one or more flash memory devices). Background technique [0002] Semiconductor memory devices, including flash memory, typically utilize memory cells to store data as electrical values, such as charge or voltage. A flash memory cell, for example, includes a single transistor with a floating gate for storing charge representing a data value. Flash memory is a non-volatile data storage device that can be electrically erased and reprogrammed. More generally, in contrast to volatile memory, which requires power to maintain stored information even when power is lost, nonvolatile memory (such as flash memory and other types of nonvolatile memory) still retains the stored information. Various approaches have been taken to facilitate increases in storage density, including: increasing the density of memory cells...

Claims

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Application Information

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IPC IPC(8): G06F12/02G11C11/56G11C16/34G11C29/02
CPCG06F12/0246G11C11/5628G11C16/349G11C29/028G06F2212/7206G06F2212/7204G06F2212/7205G06F2212/7211G11C2211/5641G11C16/00
Inventor A.塞缪尔斯W.F.克鲁格L.T.张
Owner SANDISK TECH LLC
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