System and method for rescheduling host and maintenance operations in a non-volatile memory

Patent metadata

Field	Value
Publication number	US-2017123726-A1
Application number	US-201514928649-A
Country	US
Kind code	A1
Filing date	Oct 30, 2015
Priority date	Oct 30, 2015
Publication date	May 4, 2017
Grant date	—

Abstract

Systems and methods for balancing maintenance and programming host data across multiple maintenance source blocks in a non-volatile memory are disclosed. A memory system may include non-volatile memory and a controller configured to execute one or more of the steps of selecting a fixed plurality of maintenance source blocks for executing a balance cycle of maintenance and host writes across the selected fixed plurality of maintenance source blocks. The method interleaves moving of valid data from source blocks with host data writes to achieve a balance of free space generation and consumption for the balance cycle, while periodically reevaluating an overall interleave ratio and/or substituting other previously programmed blocks for one of the previously selected plurality during the balance cycle.

First claim

We claim:

1 . A method of managing data comprising:
performing, in a non-volatile memory system having a non-volatile memory with a plurality of layers and a controller in communication with the at least one non-volatile memory, each of the plurality of layers having a different bit-per-cell data capacity, the following steps:
identifying a layer in the plurality of layers for performing a balance cycle of maintenance operations;
selecting a fixed plurality of previously programmed blocks in the identified layer for the balance cycle;
determining a balance cycle interleave ratio of host data writes to maintenance writes based on a total amount of valid data in the fixed plurality of previously programmed blocks;
initiating a maintenance operation on a first block of the fixed plurality of previously programmed blocks using the determined balance cycle interleave ratio;
at each of a plurality of predetermined scheduling points in the balance cycle of maintenance operations, determining an updated balance cycle interleave ratio based on a current remaining amount of valid data in the fixed plurality of previously programmed blocks; and
applying the updated balance cycle interleave ratio to remaining maintenance operations in the balance cycle of maintenance operations.

2 . The method of claim 1 , wherein selecting the fixed plurality of previously programmed blocks comprises selecting previously programmed blocks having a least amount of valid data.

3 . The method of claim 1 , wherein the balance cycle of maintenance operations comprises operations to move all valid data from each of the fixed plurality of previously programmed blocks selected for the balance cycle interleaved with writing an amount of host data equal to an amount of obsolete data in the plurality of previously programmed blocks such that an amount of free space created by moving the valid data from the fixed plurality of previously programmed blocks balances an amount of free space consumed by host writes during the balance cycle.

4 . The method of claim 2 , wherein determining the updated balance cycle interleave ratio comprises:
determining, when a predetermined scheduling point is reached in the balance cycle, whether a change has occurred in an amount of valid data in any of the fixed plurality of previously programmed blocks still awaiting a maintenance operation in the balance cycle; and when the change has occurred, updating the balance cycle interleave ratio to increase a ratio of host writes to maintenance writes in a remainder of the balance cycle based on the change.

5 . The method of claim 2 , wherein determining the updated balance cycle interleave ratio comprises:
determining, when a predetermined scheduling point is reached in the balance cycle, whether an amount of valid data in another previously programmed block in the layer is less than an amount of valid data in a remaining one of the fixed plurality of previously programmed blocks awaiting a maintenance operation; when the amount of valid data in the another previously programmed block is less than the amount of valid data in the remaining one, replacing the remaining one of the fixed plurality of previously programmed blocks awaiting the maintenance operation with the another previously programmed block to form a current remaining set of the fixed plurality of previously programmed blocks awaiting the maintenance operation; and determining the updated balance cycle interleave ratio based on a current remaining amount of valid data in the current remaining set; and applying the updated interleave ratio to remaining maintenance operations in the balance cycle.

6 . The method of claim 1 , wherein selecting the fixed plurality of previously programmed blocks comprises:
selecting previously programmed blocks having a least amount of valid data.

7 . The method of claim 1 , wherein non-volatile memory comprises a non-volatile memory die and the plurality of layers are contained within the non-volatile memory die.

8 . The method of claim 1 , wherein the non-volatile memory comprises an independently managed set of non-volatile memory die and the plurality of layers span across all of the non-volatile memory die in the independently managed set.

9 . The method of claim 1 , wherein the non-volatile memory comprises a three dimensional memory array.

10 . A method of managing data comprising:
performing, in a non-volatile memory system having a non-volatile memory with a plurality of layers and a controller in communication with the at least one non-volatile memory, each of the plurality of layers having a different bit-per-cell data capacity, the following steps:
selecting a fixed plurality of previously programmed blocks in in the non-volatile memory for executing a balance cycle of maintenance operations;
determining a balance cycle interleave ratio of host data writes to maintenance writes based on a total amount of valid data in the fixed plurality of previously programmed blocks;
initiating a maintenance operation on a first block of the fixed plurality of previously programmed blocks using the determined balance cycle interleave ratio; and
after initiating the maintenance operation, and in response to reaching a predetermined scheduling point in the balance cycle, the non-volatile memory system determining whether to substitute a different previously programmed block for one of the fixed plurality of previously programmed blocks.

11 . The method of claim 10 , wherein determining whether to substitute the different previously programmed block for one of the fixed plurality of previously programmed blocks comprises determining whether to substitute the different previously programmed block based on a change in an amount of valid data in the different previously programmed block.

12 . The method of claim 11 , further comprising substituting the different previously programmed block for one of the fixed plurality of previously programmed blocks when the different previously programmed blocks contains less valid data than the one of the fixed plurality.

13 . The method of claim 10 , wherein determining whether to substitute the different previously programmed block for one of the fixed plurality of previously programmed blocks comprises determining whether to substitute the different previously programmed block based on a change in an amount of valid data in one of the fixed plurality of previously programmed blocks.

14 . The method of claim 13 , further comprising substituting the different previously programmed block for one of the fixed plurality of previously programmed blocks when the amount of valid data in one of the fixed plurality decreases prior to initiating a maintenance operation on the one of the plurality.

15 . A memory system, comprising:
at least one non-volatile memory having a plurality of layers, each of the plurality of layers having a different bit-per-cell data capacity and a plurality of memory blocks; data management circuitry in communication with the non-volatile memory, the data management circuitry configured to select a fixed plurality of previously programmed blocks in one of the plurality of layers layer for a balance cycle of maintenance operations, the balance cycle comprising a set of maintenance cycles for the fixed plurality of previously programmed blocks; and program interleave circuitry configured to:
determine a balance cycle interleave ratio of host data writes to maintenance writes based on a total amount of valid data in the fixed plurality of previously programmed blocks;
upon determining the bala

Assignees

• Sandisk Technologies Inc

Inventors

• Sinclair Alan Welsh
• Gorobets Sergey Anatolievich

Classifications

• G06F3/0688

  Non-volatile semiconductor memory arrays · CPC title

• G06F3/0611

  in relation to response time · CPC title

• G06F12/02

  Addressing or allocation; Relocation (program address sequencing G06F9/00; arrangements for selecting an address in a digital store G11C8/00) · CPC title

• G06F3/0679

  Non-volatile semiconductor memory device, e.g. flash memory, one time programmable memory [OTP] · CPC title

• G06F3/0659 Primary

  Command handling arrangements, e.g. command buffers, queues, command scheduling · CPC title