# Patent

## Title
Fault detection and prediction in storage devices

## Abstract

A method of fault detection includes, while in normal operation: recording data corresponding to measurements of electrical current drawn during performance of a respective operation on a specified portion of a storage device; analyzing the recorded data, including determining whether one or more predefined characteristics of the recorded data meets predetermined failure criteria; and in accordance with a determination that the recorded data meets the predetermined failure criteria, performing one or more remedial actions, the one or more remedial actions including marking the specified portion as a known-bad portion. The method, optionally, includes, determining whether one or more predefined characteristics of the recorded data meets predetermined warning criteria and does not meet the predetermined failure criteria; and in accordance with a determination that the recorded data meets the predetermined warning criteria and does not meet predetermined failure criteria, performing one or more predictive actions.

## Background
RELATED APPLICATIONS
This application claims priority to U.S. Provisional Patent Application No. 61/955,721, filed Mar. 19, 2014, which is hereby incorporated by reference in its entirety.
This application is also related to U.S. Provisional Patent Application No. 61/955,725, filed Mar. 19, 2014, and U.S. Provisional Patent Application No. 61/955,728, filed Mar. 19, 2014, all of which are hereby incorporated by reference in their entireties.


TECHNICAL FIELD
The disclosed embodiments relate generally to memory systems, and in particular, to detecting and predicting faults in storage devices.
BACKGROUND
Semiconductor memory devices, including flash memory, typically utilize memory cells to store data as an electrical value, such as an electrical charge or voltage. A flash memory cell, for example, includes a single transistor with a floating gate that is used to store a charge representative of a data value. Flash memory is a non-volatile data storage device that can be electrically erased and reprogrammed. More generally, non-volatile memory (e.g., flash memory, as well as other types of non-volatile memory implemented using any of a variety of technologies) retains stored information even when not powered, as opposed to volatile memory, which requires power to maintain the stored information. However, it is important to protect data integrity by detecting and/or predicting faults.
SUMMARY
Various implementations of systems, methods, and devices within the scope of the appended claims each have several aspects, no single one of which is solely responsible for the attributes described herein. Without limiting the scope of the appended claims, after considering this disclosure, and particularly after considering the section entitled “Detailed Description” one will understand how the aspects of various implementations are used to detect and/or predict faults within storage devices (e.g., solid state devices). In one aspect, a storage device is configured, while in normal operation, to: (1) record data corresponding to electrical current drawn during performance of a respective operation on a specified portion of the storage device; (2) analyze the recorded data, including determining whether one or more predefined characteristics of the recorded data meets predetermined failure criteria; and (3) in accordance with a determination that the recorded data meets the predetermined failure criteria, perform one or more remedial actions, the one or more remedial actions including marking the specified portion of the storage device as a known-bad portion.



BRIEF DESCRIPTION OF THE DRAWINGS
So that the present disclosure can be understood in greater detail, a more particular description may be had by reference to the features of various embodiments, some of which are illustrated in the appended drawings. The appended drawings, however, merely illustrate the more pertinent features of the present disclosure and are therefore not to be considered limiting, for the description may admit to other effective features.
FIG. 1 is a block diagram illustrating an implementation of a data storage system in accordance with some embodiments.
FIG. 2 is a block diagram illustrating an implementation of a current monitoring module in accordance with some embodiments.
FIG. 3 is a block diagram illustrating an implementation of a current measurement circuitry in accordance with some embodiments.
FIGS. 4A-4C are diagrams of current fingerprints corresponding to various operations within a storage device in accordance with some embodiments.
FIGS. 5A-5B are diagrams of current fingerprints corresponding to erase operations in accordance with some embodiments.
FIG. 6A is a conceptual illustration of a mapping of bad portions within a storage device in accordance with some embodiments.
FIG. 6B is a conceptual illustration of a mapping of particular portions and corresponding age categories within a storage device in accordance with some embodiments.
FIG. 7 is a block diagram illustrating an implementation of a management module in accordance with some embodiments.
FIGS. 8A-8C illustrate a flowchart representation of a method of fault detection in a storage device in accordance with some embodiments.
FIGS. 9A-9C illustrate a flowchart representation of a method of fault prediction in a storage device in accordance with some embodiments.



In accordance with common practice the various features illustrated in the drawings may not be drawn to scale. Accordingly, the dimensions of the various features may be arbitrarily expanded or reduced for clarity. In addition, some of the drawings may not depict all of the components of a given system, method or device. Finally, like reference numerals may be used to denote like features throughout the specification and figures.
DETAILED DESCRIPTION
The various implementations described herein include systems, methods and/or devices used for fault detection and/or fault prediction in storage devices. Some implementations include systems, methods, and/or devices to perform a fault detection operation.
More specifically, some implementations include a method of fault detection in a storage device. In some implementations, the method includes, while in normal operation, (1) measuring electrical current drawn during performance of a respective operation on a specified portion of the storage device and recording data corresponding to the measured electrical current drawn during performance of the respective operation on the specified portion of the storage device, (2) analyzing the recorded data, including determining whether one or more predefined characteristics of the recorded data meets predetermined failure criteria, and (3) in accordance with a determination that the recorded data meets the predetermined failure criteria, performing one or more remedial actions, the one or more remedial actions including marking the specified portion of the storage device as a known-bad portion.
In some embodiments, marking the specified portion of the storage device as a known-bad portion includes updating a mapping table of the storage device to indicate that the specified portion of the storage device should not be used.
In some embodiments, the storage device includes one or more three-dimensional (3D) memory devices (e.g., memory devices blocks 134, FIG. 1), as further defined herein. In some embodiments, the 3D memory devices are coupled to a controller (e.g., storage controller 120, FIG. 1).
In some embodiments, performing the one or more remedial actions comprises: determining whether the respective operation completed; and in accordance with a determination that the respective operation did not complete, aborting the respective operation.
In some embodiments, performing the one or more remedial actions comprises: determining whether data stored in the specified portion of the storage device is valid; and in accordance with a determination that the data stored in the specified portion is valid, transferring the data stored in the specified portion of the storage device to a second portion of the storage device.
In some embodiments, the method further comprises, in accordance with a determination that the data stored in the specified portion is invalid, obtaining recovered data corresponding to the data stored in the specified portion of the storage device and storing the recovered data to a second portion of the storage device.
In some embodiments, the recorded data corresponds to a single scheduled operation, comprising the respective operation, performed by the storage device.
In some embodiments, recording data corresponding to electrical current drawn during performance of the respective operation on the specified portion of the storage device comprises recording a sequence of data corresponding to electrical current drawn during performance of the operation at a sequence of sample times.
In some embodiments, analyzing the recorded data includes one or more of: (1) determining a plurality of current peaks during the respective operation, determining one or more time intervals between said current peaks, and evaluating the time intervals in accordance with the predetermined failure criteria; (2) identifying portions of the recorded data corresponding to each of a plurality of suboperations of the respective operation; for each of a subset of the plurality of suboperations, identifying current level and/or timing parameters, and evaluating the current level and/or timing parameters in accordance with the predetermined failure criteria; (3) integrating at least a subset of the recorded sequence of data to generate a corresponding power measurement, and evaluating the generated power measurement in accordance with the predetermined failure criteria; (4) evaluating average current drawn during at least a portion of the respective operation in accordance with the predetermined failure criteria; (5) evaluating a completion time of the respective operation in accordance with the predetermined failure criteria; and (6) evaluating a difference in current drawn during two distinct portions of the respective operation in accordance with the predetermined failure criteria.
In some embodiments, the one or more predefined characteristics of the recorded data comprises at least one of: operation completion timing, cycle timing, peak current, floor current, average current, and difference current.
In some embodiments, determining whether one or more predefined characteristics of the recorded data meets predetermined failure criteria comprises: generating a score based on the one or more predefined characteristics and a plurality of predetermined target values; and determining whether the generated score meets predetermined failure criteria.
In some embodiments, the respective operation is selected from a group consisting of: a read operation, an erase operation, and a write operation.
In another aspect, any of the methods described above are performed by a storage device comprising an interface for coupling the storage device to a storage medium and a current monitoring module, the current monitoring module configured, while in normal operation, to: (1) measure electrical current drawn during performance of a respective operation on a specified portion of the storage device and record data corresponding to the measured electrical current drawn during performance of the respective operation on the specified portion of the storage device, (2) analyze the recorded data, including determining whether one or more predefined characteristics of the recorded data meets predetermined failure criteria, and (3) in accordance with a determination that the recorded data meets the predetermined failure criteria, perform one or more remedial actions, the one or more remedial actions including marking the specified portion of the storage device as a known-bad portion.
In some embodiments, the storage device comprises a storage controller and a storage medium.
In some embodiments, the storage device is configured to operate in accordance with any of the methods described above.
In yet another aspect, any of the methods described above are performed by a storage device including: (1) memory, (2) one or more processors coupled to the memory, and (3) one or more programs, stored in the memory and executed by the one or more processors, the one or more programs including instructions for performing any of the methods described above.
In yet another aspect, any of the methods described above are performed by a storage controller operable to detect faults. In some embodiments, the controller includes: (1) an interface for coupling the storage controller to a storage medium; (2) means for recording data while in normal operation, the recorded data corresponding to measurements of electrical current drawn during performance of a respective operation on a specified portion of the storage device; (3) means for analyzing the recorded data, including determining whether one or more predefined characteristics of the recorded data meets predetermined failure criteria; and (4) means for performing one or more remedial actions, in accordance with a determination that the recorded data meets the predetermined failure criteria, the one or more remedial actions including marking the specified portion of the storage device as a known-bad portion.
In yet another aspect, any of the methods described above are performed by a storage controller including an interface for operatively coupling the storage controller with a storage medium and means for performing any of the methods described herein.
In yet another aspect, some embodiments include a non-transitory computer readable storage medium, storing one or more programs for execution by one or more processors of a storage device, the one or more programs including instructions for performing any of the methods described herein.
In yet another aspect, some embodiments include a non-transitory computer readable storage medium, storing one or more programs for execution by one or more processors of a storage controller, the one or more programs including instructions for performing any of the methods described herein.
Some implementations include a method of fault prediction in a storage device. In some implementations, the method includes, while in normal operation, (1) measuring electrical current drawn during performance of a respective operation on a specified portion of the storage device and recording data corresponding to the measured electrical current drawn during performance of the respective operation on the specified portion of the storage device, (2) analyzing the recorded data, including determining whether one or more predefined characteristics of the recorded data meets predetermined warning criteria and does not meet predetermined failure criteria, and (3) in accordance with a determination that the recorded data meets the predetermined warning criteria and does not meet predetermined failure criteria, performing one or more predictive actions.
In some embodiments, the recorded data corresponds to a single scheduled operation, comprising the respective operation, performed by the storage device.
In some embodiments, the storage device includes one or more three-dimensional (3D) memory devices (e.g., memory devices blocks 134, FIG. 1), as further defined herein. In some embodiments, the 3D memory devices are coupled to a controller (e.g., storage controller 120, FIG. 1).
In some embodiments, recording data corresponding to electrical current drawn during performance of the respective operation on the specified portion of the storage device comprises recording a sequence of data corresponding to electrical current drawn during performance of the operation at a sequence of sample times.
In some embodiments, analyzing the recorded data includes one or more of: (1) determining a plurality of current peaks during the respective operation, determining one or more time intervals between said current peaks, and evaluating the time intervals in accordance with the predetermined warning criteria; (2) identifying portions of the recorded data corresponding to each of a plurality of suboperations of the respective operation; for each of a subset of the plurality of suboperations, identifying current level and/or timing parameters, and evaluating the current level and/or timing parameters in accordance with the predetermined warning criteria; (3) integrating at least a subset of the recorded sequence of data to generate a corresponding power measurement, and evaluating the generated power measurement in accordance with the predetermined warning criteria; (4) evaluating average current drawn during at least a portion of the respective operation in accordance with the predetermined warning criteria; (5) evaluating a completion time of the respective operation in accordance with the predetermined warning criteria; and (6) evaluating a difference in current drawn during two distinct portions of the respective operation in accordance with the predetermined warning criteria.
In some embodiments, the one or more predefined characteristics of the recorded data comprises at least one of: (1) operation completion timing, (2) cycle timing, (3) peak current, (4) floor current, (5) average current, and (6) difference current.
In some embodiments, determining whether one or more predefined characteristics of the recorded data meets predetermined warning criteria comprises: generating a score based on the one or more predefined characteristics and a plurality of predetermined target values; and determining whether the generated score meets predetermined warning criteria.
In some embodiments, the respective operation is selected from a group consisting of: (1) a read operation, (2) an erase operation, and (3) a write operation.
In some embodiments, the respective operation is completed successfully.
In some embodiments, performing the one or more predictive actions comprises transferring the data stored in the specified portion of the storage device to a second portion of the storage device.
In some embodiments, performing the one or more predictive actions comprises updating a mapping of the storage device to mark the specified portion as a known-bad portion.
In some embodiments, performing the one or more predictive actions comprises updating metadata corresponding to the specified portion of the storage device.
In some embodiments, updating the metadata includes flagging the specified portion of the storage device for use with low priority data only.
In some embodiments, the storage device comprises a plurality of distinct portions where each portion in the plurality of distinct portions is assigned to a respective age category of a plurality of age categories; and performing one or more predictive actions comprises reassigning the specified portion of the storage device from a current age category to an older age category in the plurality of age categories.
In another aspect, any of the methods described above are performed by a storage device comprising an interface for coupling the storage device to a storage medium and a current monitoring module, the current monitoring module configured, while in normal operation, to: (1) measure electrical current drawn during performance of a respective operation on a specified portion of the storage device and record data corresponding to the measured electrical current drawn during performance of the respective operation on the specified portion of the storage device, (2) analyze the recorded data, including determining whether one or more predefined characteristics of the recorded data meets predetermined warning criteria and does not meet predetermined failure criteria, and (3) in accordance with a determination that the recorded data meets the predetermined warning criteria and does not meet predetermined failure criteria, perform one or more predictive actions.
In some embodiments, the storage device is configured to operate in accordance with any of the methods described above.
In yet another aspect, any of the methods described above are performed by a storage device including: (1) memory, (2) one or more processors coupled to the memory, and (3) one or more programs, stored in the memory and executed by the one or more processors, the one or more programs including instructions for performing any of the methods described above.
In yet another aspect, any of the methods described above are performed by a storage device operable to predict faults. In some embodiments, the device includes: (1) an interface for coupling the storage device to a storage medium; (2) means for recording data while in normal operation, the recorded data corresponding to measurements of electrical current drawn during performance of a respective operation on a specified portion of the storage device; (3) means for analyzing the recorded data, including determining whether one or more predefined characteristics of the recorded data meets predetermined warning criteria and does not meet predetermined failure criteria; and (4) means for performing one or more predictive actions, in accordance with a determination that the recorded data meets the predetermined warning criteria and does not meet predetermined failure criteria.
In some embodiments, the storage device comprises a storage controller and a storage medium.
In yet another aspect, any of the methods described above are performed by a storage device including an interface for operatively coupling the storage device with a storage medium and means for performing any of the methods described herein.
In yet another aspect, some embodiments include a non-transitory computer readable storage medium, storing one or more programs for execution by one or more processors of a storage device, the one or more programs including instructions for performing any of the methods described herein.
In yet another aspect, some embodiments include a non-transitory computer readable storage medium, storing one or more programs for execution by one or more processors of a storage controller, the one or more programs including instructions for performing any of the methods described herein.
Numerous details are described herein in order to provide a thorough understanding of the example implementations illustrated in the accompanying drawings. However, some embodiments may be practiced without many of the specific details, and the scope of the claims is only limited by those features and aspects specifically recited in the claims. Furthermore, well-known methods, components, and circuits have not been described in exhaustive detail so as not to unnecessarily obscure more pertinent aspects of the implementations described herein.
FIG. 1 is a diagram of an implementation of data storage system 100 in accordance with some embodiments. While some example features are illustrated, various other features have not been illustrated for the sake of brevity and so as not to obscure more pertinent aspects of the example embodiments disclosed herein. To that end, as a non-limiting example, data storage system 100 includes storage controller 120, and storage medium 132, and is used in conjunction with computer system 110. In some embodiments, storage medium 132 includes a plurality of memory devices. In some embodiments, the plurality of memory devices are non-volatile memory (NVM) devices such as such as a flash memory device or a magnetic disk drive, sometimes called a hard drive. In some embodiments, the plurality of memory devices comprises memory device blocks 134 (e.g., memory devices block 134-1 through memory devices block 134-n). In some embodiments, storage medium 132 includes a single memory device or a single memory device block. In some embodiments, storage medium 132 includes NAND-type flash memory or NOR-type flash memory. In some embodiments, storage medium 132 includes one or more three-dimensional (3D) memory devices, as further defined herein. Further, in some embodiments, storage controller 120 is a solid-state drive (SSD) controller. However, one or more other types of storage media may be included in accordance with aspects of a wide variety of embodiments.
Computer system 110 is coupled to storage controller 120 through data connections 101. However, in some embodiments computer system 110 includes storage controller 120 as a component and/or a sub-system. Computer system 110 may be any suitable computer device, such as a computer, a laptop computer, a tablet device, a netbook, an internet kiosk, a personal digital assistant, a mobile phone, a smart phone, a gaming device, a computer server, or any other computing device. Computer system 110 is sometimes called a host or host system. In some embodiments, computer system 110 includes one or more processors, one or more types of memory, a display and/or other user interface components such as a keyboard, a touch screen display, a mouse, a track-pad, a digital camera and/or any number of supplemental devices to add functionality.
In some embodiments, computer system 110 includes: one or more processing units (CPUs) for executing modules, programs and/or instructions stored in memory and thereby performing processing operations; memory; one or more network interfaces; and one or more communication buses for interconnecting these components. The one or more communication buses, optionally, include circuitry (sometimes called a chipset) that interconnects and controls communications between system components. Computer system 110 is operatively coupled with data storage system 100 by one or more communication buses. In some embodiments, computer system 110 also includes a user interface. The user interface includes one or more output devices that enable presentation of media content, including one or more speakers and/or one or more visual displays. The user interface also includes one or more input devices, including user interface components that facilitate user input such as a keyboard, a mouse, a voice-command input unit or microphone, a touch screen display, a touch-sensitive input pad, a gesture capturing camera, or other input buttons or controls. The memory includes high-speed random access memory, such as DRAM, SRAM, DDR RAM or other random access solid state memory devices, and may include non-volatile memory, such as one or more magnetic disk storage devices, optical disk storage devices, flash memory devices, or other non-volatile solid state storage devices. The memory, optionally, includes one or more storage devices remotely located from one or more CPUs. The memory, or alternatively the non-volatile memory device(s) within the memory, comprises a non-transitory computer readable storage medium. In some embodiments, the memory, or the non-transitory computer readable storage medium of the memory, stores the following programs, modules, and data structures, or a subset or superset thereof:

    
    
        an operating system including procedures for handling various basic system services and for performing hardware dependent tasks;
        a network communication module for connecting computer system 100 to data storage system 110 connected to one or more networks via one or more network interfaces (wired or wireless);
        a presentation module for enabling presentation of information (e.g., a user interface for a web page or an application program, audio and/or video content, text, etc.) at computer system 110 via one or more output devices (e.g., displays, speakers, etc.) associated with the user interface;
        an input processing module for detecting one or more user inputs or interactions from one of the one or more input devices and interpreting the detected input or interaction;
        a memory command module for issuing memory commands (e.g., read, write, and erase commands) to storage controller 120; and
        a management module for persisting data, including but not limited to:
        
            a log entry module for generating a log entry associated with respective write data; and
            recovery module for performing a recovery process, or causing a recovery process to be performed, in response to detecting an error condition or synchronization command;
        
        
        optionally, one or more applications, such as one or more applications for providing services to client systems or other users of computer system 110, and which utilize storage medium 132, via storage controller 120, to persistently store data utilized by the one or more applications.
    
    


Storage medium 132 is coupled to storage controller 120 through connections 103 and 105. Connections 103 are sometimes called data connections, but typically convey commands in addition to data, and optionally convey metadata, error correction information and/or other information in addition to data values to be stored in storage medium 132 and data values read from storage medium 132. In some embodiments, however, storage controller 120 and storage medium 132 are included in the same device as components thereof. Furthermore, in some implementations storage controller 120 and storage medium 132 are embedded in a host device, such as a mobile device, tablet, other computer or computer controlled device, and the methods described herein are performed by the embedded storage controller. Storage medium 132 may include any number (i.e., one or more) of memory devices including, without limitation, non-volatile semiconductor memory devices, such as flash memory. As a non-limiting example, flash memory devices can be configured for enterprise storage suitable for applications such as cloud computing, or for caching data stored (or to be stored) in secondary storage, such as hard disk drives. Additionally and/or alternatively, flash memory can also be configured for relatively smaller-scale applications such as personal flash drives or hard-disk replacements for personal, laptop and tablet computers.
In some embodiments, storage medium 132 is a persistent datastore (e.g., comprising non-volatile memory such as flash memory), and storage medium 132 includes a plurality of records 132 each including write data and a corresponding log entry. In some embodiments, each record corresponds to a transaction (e.g., a write operation) against the persistent datastore. In some embodiments, storage medium 132 also includes a log stream 134 comprising a plurality of log stream portions, where each log stream portion includes a log entry collection (e.g., 256 log entries). In some embodiments, storage medium 132 further includes one or more datastore snapshots 136. In some embodiments, each of one or more datastore snapshots 136 corresponds to the state(s) of one or more datastore tables at a point in time, where the one or more datastore tables enable the host to access data stored in the persistent datastore. For example, a snapshot of the one or more datastore tables is generated every N transactions (e.g., N=1000, 10000, etc.).
In some embodiments, storage medium 132 is divided into a number of addressable and individually selectable blocks (e.g., memory devices block 134-1). In some embodiments, the individually selectable blocks are the minimum size erasable units in a flash memory device. In other words, each block contains the minimum number of memory cells that can be erased simultaneously. Each block is usually further divided into a plurality of pages and/or word lines, where each page or word line is typically an instance of the smallest individually accessible (readable) portion in a block. In some embodiments (e.g., using some types of flash memory), the smallest individually accessible unit of a data set, however, is a sector, which is a subunit of a page. That is, a block includes a plurality of pages, each page contains a plurality of sectors, and each sector is the minimum unit of data for reading data from the flash memory device. For example, one block comprises any number of pages, for example, 64 pages, 128 pages, 256 pages or another suitable number of pages. Blocks are typically grouped into a plurality of planes and/or zones. Each block plane or zone can be independently managed to some extent, which increases the degree of parallelism for parallel operations and simplifies management of storage medium 132.
In some embodiments, storage medium 132 includes metadata corresponding to respective portions of storage medium 132 (e.g., blocks, portions, pages, sectors, zones, and/or planes). In some embodiments, the metadata includes information regarding the health and/or age of the corresponding portion of storage medium 132 (e.g., an estimate of how many erase cycles may be performed before the portion fails). In some embodiments, storage medium 132 includes a mapping of known-bad portions of storage medium 132 (e.g., known-bad portions). In some embodiments, storage medium 132 includes a mapping of good portions of storage medium 132 (e.g., a mapping that excludes known-bad portions). In some embodiments, the metadata and/or mapping is stored in management module 121 (e.g., instead of storing in storage medium 132 or in addition to storing in storage medium 132).
In some embodiments, storage controller 120 includes management module 121, input buffer 123, output buffer 124, error control module 125, memory command and data interface 128, and current monitoring module 130. Storage controller 120 may include various additional features that have not been illustrated for the sake of brevity and so as not to obscure more pertinent features of the example embodiments disclosed herein, and that a different arrangement of features may be possible. Input and output buffers 123, 124 provide an interface to computer system 110 through data connections 101. Similarly, memory command and data interface 128 provides an interface to storage medium 132 though connections 103. In some embodiments, memory command and data interface 128 includes read and write circuitry, including circuitry capable of providing reading signals to storage medium 132 (e.g., reading threshold voltages for NAND-type flash memory). As will be discussed in greater detail below with reference to FIG. 2, current monitoring module 130 monitors electrical current flow across various components of storage medium 132 via connections 105.
In some embodiments, management module 121 includes one or more processing units (CPU(s), also sometimes called one or more processors) 122 configured to execute instructions in one or more programs (e.g., in management module 121). In some embodiments, one or more CPUs 122 are shared by one or more components within, and in some cases, beyond the function of storage controller 120. Management module 121 is coupled to input buffer 123, output buffer 124 (connection not shown), error control module 125, memory command and data interface 128, and current monitoring module 130 in order to coordinate the operation of these components.
Error control module 125 is coupled to memory command and data interface 128, input buffer 123 and output buffer 124. Error control module 125 is provided to limit the number of uncorrectable errors inadvertently introduced into data. In some embodiments, error control module 125 is executed in software by one or more CPUs 122 of management module 121, and, in other embodiments, error control module 125 is implemented in whole or in part using special purpose circuitry to perform encoding and decoding functions. To that end, error control module 125 includes an encoder 126 and a decoder 127. Encoder 126 encodes data by applying an error control code to produce a codeword, which is subsequently stored in storage medium 132.
When the encoded data (e.g., one or more codewords) is read from storage medium 132, decoder 127 applies a decoding process to the encoded data to recover the data, and to correct errors in the recovered data within the error correcting capability of the error control code. Those skilled in the art will appreciate that various error control codes have different error detection and correction capacities, and that particular codes are selected for various applications for reasons beyond the scope of this disclosure. As such, an exhaustive review of the various types of error control codes is not provided herein. Moreover, those skilled in the art will appreciate that each type or family of error control codes may have encoding and decoding algorithms that are particular to the type or family of error control codes. On the other hand, some algorithms may be utilized at least to some extent in the decoding of a number of different types or families of error control codes. As such, for the sake of brevity, an exhaustive description of the various types of encoding and decoding algorithms generally available and known to those skilled in the art is not provided herein.
During a write operation, input buffer 123 receives data to be stored in storage medium 132 from computer system 110 (e.g., write data). The data held in input buffer 123 is made available to encoder 126, which encodes the data to produce one or more codewords. The one or more codewords are made available to memory command and data interface 128, which transfers the one or more codewords to storage medium 132 in a manner dependent on the type of storage medium being utilized.
A read operation is initiated when computer system (host) 110 sends one or more host read commands on control line 111 to storage controller 120 requesting data from storage medium 132. Storage controller 120 sends one or more read access commands to storage medium 132, via memory command and data interface 128, to obtain raw read data in accordance with memory locations (addresses) specified by the one or more host read commands. Memory command and data interface 128 provides the raw read data (e.g., comprising one or more codewords) to decoder 127. If the decoding is successful, the decoded data is provided to output buffer 124, where the decoded data is made available to computer system 110. In some embodiments, if the decoding is not successful, storage controller 120 may resort to a number of remedial actions or provide an indication of an irresolvable error condition.
FIG. 2 is a block diagram illustrating an implementation of current monitoring module 130 in accordance with some embodiments. Current monitoring module 130 typically includes: current module 202 for monitoring current in storage medium 132, control module 204 to coordinate the operation of other components and/or modules, power supply module 206 to supply power to storage medium 132, and switching network 208 to operably couple current module 202 and power supply module 206 to various portions of storage medium 132. In some embodiments, control module 204 coordinates the operation of other components (e.g., switching network 208 and current module 202) by executing instructions from management module 121 and/or computer system 110 (FIG. 1). In some embodiments, one or more functions (e.g., initiating a remedial action) described herein as being performed by control module 204 are instead performed by management module 121 of storage controller 120.
Switching network 208 comprises a plurality of switches (also sometimes called sense switches). The switches are, optionally, implemented via transistors, transmission gates, and the like. In some embodiments, the configuration of switching network 208 is determined by control module 204. In some embodiments, the configuration of switching network 208 is determined by management module 121 (FIG. 1).
Power supply module 206 provides power via switching network 208 to various components in storage medium 132 (e.g., memory device 212-1 through memory device 212-m). In some embodiments, control module 204 coordinates the operation of power supply module 206. In some embodiments, power supply module 206 provides power only to components of storage medium 132 that are coupled to current module 202. In other embodiments, power supply module 206 provides power to components of storage medium 132 that are not coupled to current module 202.
In some embodiments, current module 202 includes one or more sense amplifiers (not shown) for amplifying output from storage medium 132. In some embodiments, current module 202 includes resistor network 210 for adjusting gain across the inputs of current module 202. In some embodiments, current module 202 includes current measurement circuitry 211 for measuring current usage in storage medium 132. In some embodiments, current module 202 includes measurement circuitry (e.g., measurement circuitry 211) and software for measuring, analyzing, and/or recording the current drawn. Current module 202 monitors the current usage by various components of storage medium 132 (e.g., memory device 212-1 through memory device 212-m) via switching network 208. In some embodiments, the current data obtained by current module 202 is stored in memory (e.g., in management module 121 and/or storage medium 132). In some embodiments, current module 202 monitors and, optionally, records power usage by various components of storage medium 132.
In some embodiments, resistor network 210 includes one or more resistors (also sometimes called sense resistors) configured such that at least a subset of the one or more resistors is coupled to an output of storage medium 132. In some embodiments, the configuration of resistor network 210 is determined by control module 204. In some embodiments, at a given time during operation, control module 204 determines the configuration of resistor network 210 based on the particular portion of storage medium 132 connected to current module 202 via switching network 208.
In some embodiments, switching network 208 is configured (e.g., configured by control module 204) such that current module 202 is coupled to a first portion of storage medium 132 (e.g., memory devices 212) and power supply module 206 is coupled to a second portion of storage medium 132 (e.g., memory devices 212 and memory devices 214).
Current monitoring module 130 may include various additional features that have not been illustrated for the sake of brevity and so as not to obscure more pertinent features of the example embodiments disclosed herein, and that a different arrangement of features may be possible. For example, in some embodiments, current monitoring module 130 further includes memory for recording electrical current data. In some embodiments, current monitoring module 130 includes other combinations of hardware (e.g., current measurement circuitry 211) and software (e.g., programs) for monitoring and/or recording electrical current data.
Although FIG. 2 shows current monitoring module 130 and storage medium 132, FIG. 2 is intended more as functional descriptions of the various features which may be present in a management module, than as a structural schematic of the embodiments described herein. In practice, and as recognized by those of ordinary skill in the art, the programs, modules, and data structures shown separately could be combined and some programs, modules, and data structures could be separated.
FIG. 3 is a block diagram illustrating an implementation of current module 202 in accordance with some embodiments. Current measurement circuitry 211 typically includes circuitry for measuring instantaneous current and peak current and, optionally, includes circuitry for measuring average current, level-adjusted current, and various power measurements (not shown). Current measurement circuitry 211 is coupled to storage medium 132 via inputs 301. In some embodiments, current measurement circuitry 211 receives reset 303 and/or reference voltage 336 from control module 204.
In some embodiments, inputs 301 are coupled to one or more resistors in resistor network 210. For example, in some embodiments, resistor network 210 includes resistor R1 and is configured such that resistor R1 is coupled to the output of storage medium 132 via switching network 208. In this example, inputs 301 are coupled to opposite ends of resistor R1 such that comparator 302 measures the current across resistor R1.
Instantaneous current data is obtained from output 330 of amplifier 304. The first input of amplifier 304 is coupled to the output of comparator 302 and the second input of amplifier 304 is coupled to reference voltage 305. In some embodiments, current measurement circuitry 211 measures instantaneous current and other modules (e.g., current module 202) calculate average current, peak current, and/or level-adjusted current based on the measured instantaneous current.
Average current data is obtained from output 332 of integrator 306. In some embodiments, integrator 306 includes amplifier 308, resistor 309, capacitor 310, and reference voltage 307. In these embodiments, the first input of amplifier 308 is coupled to the output of comparator 302 via resistor 309; the second input of amplifier 308 is coupled to reference voltage 307; and output 332 of amplifier 308 is coupled to the first input of amplifier 308 via capacitor 310.
Peak current data is obtained from output 334 of sample and hold 311. In some embodiments, sample and hold 311 includes amplifier 321, reference voltages 326 and 328, capacitor 322, switch 324, and diode 320. In these embodiments, the first input of amplifier 312 is coupled to the output of comparator 302; the second input of amplifier 312 is coupled to output 334; the output of amplifier 312 is coupled to output 334 via diode 320; reference voltage 328 is coupled to output 334 via capacitor 322; and reference voltage 326 is coupled to output 334 via switch 324. In some implementations, reference voltage 326 is reference voltage 382.
Level-adjusted current is obtained from output 338 of level adjustor 315. In some embodiments, level adjustor 315 includes digital-to-analog-convertor (DAC) 314, amplifier 316, and latch 318. In these embodiments, the first input of amplifier 316 is coupled to the output of comparator 302; the second input of amplifier 316 is coupled to the output of DAC 314; the input of DAC 314 is connected to reference voltage 336; the output of amplifier 316 is coupled to the input of latch 318; and the output of latch 318 is coupled to output 338.
FIGS. 4A-4C are diagrams of current fingerprints corresponding to various operations within a storage device in accordance with some embodiments. As used herein, a current “fingerprint” means a trace of the electrical current drawn during a respective operation in a storage device (e.g., within storage medium 132, FIG. 1). The current fingerprints shown in FIGS. 4A-4C represent current drawn versus time elapsed for three distinct operations. A current curve during a respective operation (and a current curve during a particular phase of the respective operation) is predictable when the device is operating properly. The current curve determined from measurements of a successful operation is, optionally, used to determine target current values for use when analyzing the electrical current drawn by future operations of the same type. The y-axis of each of FIGS. 4A-4C represents current and the x-axis represents elapsed time.
The diagram in FIG. 4A corresponds to a multi-plane read operation (e.g., a read operation involving both plane 1 and plane 2). Phase 404 corresponds to reading data from storage medium 132 (e.g., reading data from memory devices 212-1 through 212-m in FIG. 2). Phases 406 and 410 correspond to data transfer from plane 1 and phases 408 and 412 correspond to data transfer from plane 2. In some embodiments, average and peak current measurements are determined for each phase of the multi-plan read operation. In some embodiments, difference current between the planes is calculated by subtracting the average current corresponding to a first phase from the average current corresponding to a second phase (e.g., subtracting the average current corresponding to phase 408 from the average current corresponding to phase 406). In some embodiments, power corresponding to a particular phase is determined by integrating under the current curve for that phase (e.g., integrating the current curve in phase 404). In some embodiments, total time to complete a particular phase of the operation (e.g., phase 404) and/or total time to complete the operation is determined. The diagram in FIG. 4B corresponds to a write operation. Phases 440 correspond to data transfer to storage medium 132 and phases 442 correspond to data hardening within storage medium 132. The diagram in FIG. 4C corresponds to a non-transfer erase operation (e.g., the particular erase operation involves no data transfer). Phases 420 correspond to particular passes of the erase operation (e.g., phase 420-1 corresponds to the first pass). Phase 424 corresponds to the completion of the erase operation.
FIGS. 5A-5B are diagrams of current fingerprints corresponding to erase operations in accordance with some embodiments. The y-axis of each of FIGS. 5A-5C represents current and the x-axis represents elapsed time. FIG. 5A corresponds to a successful erase operation (e.g., a normal erase operation). FIG. 5B corresponds to a failed erase operation. Average current, peak current, phase completion time, operation completion time, and peak spacing are, optionally, used to determine that the erase operation in FIG. 5B has failed.
FIG. 6A is a conceptual illustration of mapping 600 in accordance with some embodiments. Mapping 600 maps memory 602 in a storage medium (e.g., storage medium 132 in FIG. 1). In some embodiments, mapping 600 is a logical to physical mapping (e.g., mapping 722 in FIG. 7). Known-bad portions 604-1 and 604-2 are marked in mapping 600. In some embodiments, known-bad portions 604 are excluded from mapping 600.
FIG. 6B is a conceptual illustration of mapping 610 in accordance with some embodiments. Mapping 610 maps particular portions within a storage medium (e.g., storage medium 132) and their corresponding age categories. In some embodiments, mapping 610 is a logical to physical mapping (e.g., mapping 722 in FIG. 7) that includes data corresponding to the respective age category for each physical portion.
FIG. 7 is a block diagram illustrating an implementation of management module 121 in accordance with some embodiments. Management module 121 typically includes: one or more processing units (CPUs) 122 for executing modules, programs and/or instructions stored in memory 702 and thereby performing processing operations; memory 702; and one or more communication buses 704 for interconnecting these components. One or more communication buses 704, optionally, include circuitry (sometimes called a chipset) that interconnects and controls communications between system components. Management module 121 is operatively coupled with buffer 123, buffer 124, error control module 125, current monitoring module 130, and storage medium 132 (e.g., through memory command and data interface 128) by one or more communication buses 704. Memory 702 includes high-speed random access memory, such as DRAM, SRAM, DDR RAM or other random access solid state memory devices, and may include non-volatile memory, such as one or more magnetic disk storage devices, optical disk storage devices, flash memory devices, or other non-volatile solid state storage devices. In some embodiments, memory 702 includes volatile data 714 corresponding to portions of storage medium 132. In some embodiments, memory 702 comprises metadata 716 (e.g., metadata comprising age category, known-bad portion, etc.) corresponding to portions of storage medium 132. Memory 702, optionally, includes one or more storage devices remotely located from one or more CPUs 122. Memory 702, or alternatively the non-volatile memory device(s) within memory 702, comprises a non-transitory computer readable storage medium. In some embodiments, memory 702, or the non-transitory computer readable storage medium of memory 702, stores the following programs, modules, and data structures, or a subset or superset thereof:

    
    
        data read module 706 for performing a read operation to read data from storage medium 132 (e.g., a persistent data store including non-volatile memory such as flash memory) according to a read command from computer system 110;
        data write module 708 for performing a write operation to write data (e.g., a record including write data and a log entry) to storage medium 132 according to a write command from computer system 110;
        data erase module 710 for performing an erase operation to erase data from storage medium 132 according to an erase command from computer system 110;
        log entry module 712 for generating a log entry associated with respective write data;
        recovery module 718 for performing a recovery process, or causing a recovery process to be performed, in response to detecting an error condition or synchronization command;
        transfer module 720 that is used for transferring data held in volatile memory to non-volatile memory; and
        logical to physical mapping 722, which maps logical addresses to physical addresses for respective portions of storage medium 132, and optionally also maps physical addresses for respective portions of storage medium 132 to logical addresses. In some embodiments, logical to physical mapping 722 excludes known-bad portions of storage medium 132 from the maps.
    
    


Each of the above identified elements may be stored in one or more of the previously mentioned memory devices, and corresponds to a set of instructions for performing a function described above. The above identified modules or programs (i.e., sets of instructions) need not be implemented as separate software programs, procedures or modules, and thus various subsets of these modules may be combined or otherwise re-arranged in various embodiments. In some embodiments, memory 702 stores a subset of the modules and data structures identified above. Furthermore, memory 702 may store additional modules and data structures not described above. In some embodiments, the programs, modules, and data structures stored in memory 702, or the non-transitory computer readable storage medium of memory 2702, provide instructions for implementing any of the methods described below with reference to FIGS. 8A-8C and/or FIGS. 9A-9C.
Although FIG. 7 shows management module 121, FIG. 7 is intended more as functional descriptions of the various features which may be present in a management module, than as a structural schematic of the embodiments described herein. In practice, and as recognized by those of ordinary skill in the art, the programs, modules, and data structures shown separately could be combined and some programs, modules, and data structures could be separated.
FIGS. 8A-8C illustrate a flowchart representation of method 800 of fault detection in a storage device, in accordance with some embodiments. In some embodiments, the storage device comprises a dual in-line memory module (DIMM) device. In some implementations, the storage device is compatible with a DIMM memory slot. For example, in some implementations, the storage device is compatible with a 240-pin DIMM memory slot using a DDR3 interface specification. In some implementations, the storage device comprises a storage controller (e.g., storage controller 120, FIG. 1) and a storage medium (e.g., storage medium 132, FIG. 1). In some implementations, the storage device coordinates and manages multiple sub-system components to detect faults, which initiates performance of method 800. At least in some implementations, method 800 is performed by a storage controller (e.g., storage controller 120, FIG. 1) or one or more components of the storage controller (e.g., management module 121 and/or current monitoring module 130, FIG. 1). In some embodiments, method 800 is governed by instructions that are stored in a non-transitory computer readable storage medium and that are executed by one or more processors of a device, such as the one or more processors 122 of management module 121, as shown in FIG. 1.
While in normal operation (802), the storage device records (804) data corresponding to electrical current drawn during performance of a respective operation on a specified portion of the storage device (e.g., by measuring electrical current drawn during performance of the respective operation on the specified portion of the storage device and recording data corresponding to the measured electrical current drawn during performance of the respective operation on the specified portion of the storage device). In some implementations, the electrical current is determined and/or obtained in a current monitoring module (e.g., current monitoring module 130, FIG. 1) and recorded in memory. In some implementations, the storage device records the data in a management module (e.g., in memory 702, FIG. 7). In some implementations the storage device records the data in a storage medium (e.g., storage medium 132, FIG. 1). In some implementations, the specified portion of the storage device is specified by a host system (e.g., computer system 110, FIG. 1) and is operably coupled to the current monitoring module via a switching network (e.g., switching network 208, FIG. 2). For example, referring to FIG. 2, in some implementations, the specified portion is a subset of memory devices 212 and the subset is coupled to current module 202 (e.g., is coupled to a resistor in resistor network 210) via switching network 208. In this example, power supply module 206 is coupled to the subset of memory devices 212 and is, optionally, coupled to other memory devices (e.g., memory devices 214) via switching network 208. Also, in this example, the configurations of switching network 208 and resistor network 210 are controlled by control module 204. In some implementations, the respective operation corresponds to a command sent from the host system. In some implementations, recording data corresponding to electrical current drawn during performance of a respective operation on a specified portion of the storage device comprises recording one or more outputs of current measurement circuitry (e.g., outputs 330, 332, 334, and 338 of current measurement circuitry 211 in FIG. 3). In some embodiments, the specified portion of the storage device includes, or is included in, one or more three-dimensional (3D) memory devices (e.g., memory device 212-1, FIG. 2).
As used herein, “normal” operation, also sometimes called “standard” operation, is a mode of operation of the storage device in which the storage system is being used for its intended purposes (e.g., to read and write data) by a host system (e.g., computer system 110, FIG. 1). For example, in normal operation, the storage device is receiving and responding to commands sent from a host system. In some implementations, the storage device operates in one of a plurality of modes, where the plurality of modes includes a normal mode (e.g., the mode used during normal operation) and a testing mode. Normal operation is distinguished from manufacturing of the storage device, which is completed prior to the storage device being coupled to a host system. Normal operation is also distinguished from testing of the storage device (sometimes called a testing mode of operation), which is either done: (1) while coupled to a testing system; (2) prior to being coupled to a host system; and/or (3) is done in a manner that prevents the storage device from being used for its intended purposes during the testing process. For example, failure detection optionally occurs in a storage device during manufacturing, testing, and normal operation. In some implementations, failure detection during the manufacturing process comprises detecting that the storage device (and/or individual components therein) do not meet manufacturing parameters (e.g., one or more characteristics of the device are outside of predetermined acceptable boundaries). In some implementations, failure detection during a testing process comprises testing the operability of a plurality of distinct portions on the storage device (e.g., systematically testing each portion of the storage device in a controlled manner). In some implementations, the testing process includes more controlled parameters than normal operation. For example, during the testing process, write commands optionally involve known predetermined data to be written to each portion, whereas during normal operation, the data is variable and is based in part on the operation of the host system.
In some embodiments, the recorded data corresponds (806) to a single scheduled operation, comprising the respective operation, performed by the storage device. For example, the storage device receives one or more commands from a host system and schedules corresponding operations such that electrical current data associated with the respective operation is not obscured and/or influenced by electrical current data associated with other operations. In some implementations, the recorded data corresponds to electrical current drawn solely by performance of the respective operation on the specified portion of the storage device. In some implementations, the respective operation comprises a memory access or erase operation and the electrical current measured does not include electrical current drawn by any other memory access or erase operations. For example, the respective operation is scheduled such that the portion of the storage device for which drawn current is measured has no scheduled overlapping operations.
In some embodiments, recording data corresponding to electrical current drawn during performance of the respective operation on the specified portion of the storage device comprises recording (808) a sequence of data corresponding to electrical current drawn during performance of the operation at a sequence of sample times. In some implementations, the sequence of data is generated by recording electrical current every 10 microseconds during a respective operation (e.g., an operation lasting 1500 microseconds). For example, in some implementations, data is recorded during the multi-plane write operation illustrated in FIG. 4A such that multiple data points (e.g., 5 data points, 50 data points, or 500 data points) are recorded during each phase (e.g., each of phases 404, 406, 408, 410, and 412 in FIG. 4A) of the operation.
In some embodiments, the respective operation is selected (810) from a group consisting of: a read operation; an erase operation; and a write operation. For example, a read operation reads data stored in the specified portion of the storage device; a write operation writes data to the specified portion of the storage device; and an erase operation erases any data stored in the specified portion of the storage device. In some implementations, a read operation is a multi-plane read operation. In some implementations, the write operation comprises a program operation. In some implementations, the respective operation is a combination of read, write, and/or erase operations. In some implementations, the respective operation comprises additional suboperations (e.g., data hardening, error correction, and/or metadata updating). In some implementations, detection of a fault in a specified portion of the storage device depends on the respective operation. For example, a fault is detected during performance of a write operation on a specified portion of the storage device, but a fault is not detected during performance of a read operation on the specified portion.
The storage device analyzes (812) the recorded data, including determining whether one or more predefined characteristics of the recorded data meets predetermined failure criteria. In some implementations, analyzing the recorded data comprises comparing one or more predefined characteristics of the recorded data with one or more predefined characteristics of recorded data from a previous operation on the same portion. In some implementations, analyzing the recorded data comprises comparing one or more predefined characteristics of the recorded data with one or more predefined characteristics of recorded data from an operation on a different portion of the storage device. In some implementations, analyzing the recorded data comprises comparing one or more predefined characteristics of the recorded data with one or more preset boundaries. In some implementations, analyzing the recorded data comprises analyzing data corresponding to one or more outputs of current measurement circuitry (e.g., outputs 330, 332, 334, and 338 of current measurement circuitry 211 in FIG. 3).
In some embodiments, the one or more predefined characteristics of the recorded data comprises (814) at least one of: operation completion timing; cycle timing; peak current; floor current; average current; and difference current. For example, in FIG. 4A, operation completion timing is the time elapsed as phase 412 (i.e., the final phase of the operation) completes. Peak current, optionally, comprises the peak current (e.g., maximum current) during the entire operation (e.g., in FIG. 4A the peak current for the operation is obtained in phase 404) and/or the peak current for a particular phase of the operation (e.g., the peak current during phase 406 in FIG. 4A). Floor current, optionally, comprises the floor current (e.g., minimum current) during a particular phase of the operation and/or the floor current of the entire operation. Average current, optionally, comprises the average current during a particular phase of the operation (e.g., average current during phase 410 in FIG. 4A) and/or the average current of the entire operation. In some implementations, difference current comprises a current difference between two phases of the operation (e.g., the difference in average current between phases 406 and 408 in FIG. 4A). In some implementations, difference current comprises a current difference between operations on different portions of the storage device (e.g., different blocks, planes, or die of the storage device). For example, the difference in current between current drawn during a read operation performed on memory devices block 134-1 and current drawn during a read operation performed on memory devices block 134-n in FIG. 1. In some implementations, cycle timing is the time elapsed during a particular phase (e.g., phase 410) of the operation. In some implementations, cycle timing is the timing between successive current peaks during the operation (e.g., the timing between successive peaks in phase 442-3 in FIG. 4B).
In some embodiments, determining whether one or more predefined characteristics of the recorded data meets predetermined failure criteria comprises (816): generating a score based on the one or more predefined characteristics and a plurality of predetermined target values; and determining whether the generated score meets predetermined failure criteria. For example, a predetermined target value is associated with each of the one or more predefined characteristics and the score is generated by adding the difference between each characteristic's recorded value and target value. In this example, if the generated score exceeds a predetermined limit then the score meets predetermined failure criteria. In some implementations, a particular weighting factor is associated with each predefined characteristic of the one or more predefined characteristics.
In some embodiments, analyzing the recorded data includes (818) one or more of: determining a plurality of current peaks during the respective operation, determining one or more time intervals between said current peaks, and evaluating the time intervals in accordance with the predetermined failure criteria (e.g., in FIG. 4B, determining one or more time intervals between current peaks comprises determining the time interval between current peaks in phase 442-3 and/or phase 442-3); identifying portions of the recorded data corresponding to each of a plurality of suboperations (e.g., phases) of the respective operation; for each of a subset of the plurality of suboperations, identifying current level and/or timing parameters, and evaluating the current level and/or timing parameters in accordance with the predetermined failure criteria (e.g., in FIG. 4A, identifying portions of the recorded data corresponding to each of a plurality of suboperations comprises identifying phases 404, 406, 408, 410, and 412); integrating at least a subset of the recorded sequence of data to generate a corresponding power measurement, and evaluating the generated power measurement in accordance with the predetermined failure criteria (e.g., in FIG. 4A, integrating at least a subset of the recorded sequence of data to generate a corresponding power measurement comprises integrating the current in phase 404 to generate total power during the phase); evaluating average current drawn during at least a portion of the respective operation in accordance with the predetermined failure criteria (e.g., in FIG. 4A, evaluating average current drawn during at least a portion of the respective operation comprises evaluating average current drawn during phase 406); evaluating a completion time of the respective operation in accordance with the predetermined failure criteria (e.g., in FIG. 4A, evaluating a completion time of the respective operation comprises evaluating the elapsed time as phase 412 completes); and evaluating a difference in current drawn during two distinct portions (e.g., phases) of the respective operation in accordance with the predetermined failure criteria (e.g., in FIG. 4A, evaluating a difference in current drawn during two distinct portions of the respective operation comprises evaluating the difference in current drawn during phase 406 and phase 408). In some implementations, the predetermined failure criteria, optionally, includes failure criteria with respect to the one or more time intervals, suboperations, phases, and/or portions of the respective operation.
In accordance with a determination that the recorded data meets the predetermined failure criteria, the storage device performs (820) one or more remedial actions, the one or more remedial actions including marking the specified portion of the storage device as a known-bad portion. In some implementations, marking the specified portion of the storage device as a known-bad portion comprises generating and/or updating metadata corresponding to the specified portion. In some implementations, a portion marked as a known-bad portion is excluded from future operations. In some implementations, the one or more remedial actions comprise adjusting one or more parameters associated with the specified portion (e.g., adjusting a voltage source supplied to the specified portion and/or adjusting clock timing supplied to the specified portion). In some implementations, the one or more remedial actions are coordinated by a management module (e.g., management module 121, FIG. 1). In some implementations, the one or more remedial actions comprise updating metadata corresponding to the specified portion of the storage device, including updating the metadata to mark the specified portion of the storage device as a known-bad portion.
In some embodiments, marking the specified portion of the storage device as a known-bad portion includes updating (822) a mapping table of the storage device to indicate that the specified portion of the storage device should not be used. For example, mapping 600 in FIG. 6A indicates that portions 604-1 and 604-2 are known-bad portions. In this example, portions 604-1 and 604-2 are not used in operations after being marked as known-bad portions. In some implementations, the mapping table is stored in a storage medium (e.g., storage medium 132, FIG. 1). In some implementations, the mapping table is stored in a management module (e.g., memory 702 of management module 121, FIG. 7). In some implementations, the mapping table is a logical memory to physical memory mapping (e.g., logical to physical mapping 722, FIG. 7).
In some embodiments, performing the one or more remedial actions comprises (824): determining whether the respective operation completed; and in accordance with a determination that the respective operation did not complete, aborting the respective operation. For example, FIG. 5B illustrates an erase operation that has not completed. In this example, the erase operation in FIG. 5B would be aborted. In some implementations, a memory command and data interface (e.g., memory command and data interface 128, FIG. 1) aborts the respective operation.
In some embodiments, performing the one or more remedial actions comprises (826): determining whether data stored in the specified portion of the storage device is valid; and in accordance with a determination that the data stored in the specified portion is valid, transferring the data stored in the specified portion of the storage device to a second portion of the storage device. For example, the specified portion of the storage device is a memory block (e.g., memory devices block 134-1, FIG. 1) and transferring the data stored in the specified portion to a second portion comprises transferring the data to a second memory block (e.g., memory devices block 134-n, FIG. 1). In some implementations, determining whether data stored in the specified portion of the storage device is valid comprises executing a read operation and evaluating the read data (e.g., comparing the read data with data from another source). In some implementations, determining whether data stored in the specified portion of the storage device is valid comprises evaluating metadata associated with the specified portion (e.g., a hash and/or checksum associated with the specified portion). In some implementations, an error control module (e.g., error control module 125, FIG. 1) determines whether data stored in the specified portion of the storage device is valid.
In some embodiments, in accordance with a determination that the data stored in the specified portion is invalid, the storage device obtains (828) recovered data corresponding to the data stored in the specified portion of the storage device and storing the recovered data to a second portion of the storage device. In some implementations, the storage device obtains recovered data from volatile memory (e.g., memory 702 in FIG. 7). In some implementations, the storage device obtains recovered data from a different portion of a storage medium (e.g., storage medium 132, FIG. 1). In some implementations, the recovered data comprises a previous version of the data stored in the specified portion.
In some embodiments, in accordance with a determination that the recorded data does not meet the predetermined failure criteria, the storage device determines whether or not the recorded data meets predetermined warning criteria; and, in accordance with a determination that the recorded data meets the predetermined warning criteria, the storage device performs one or more predictive actions. For additional details regarding this aspect of method 800 refer to the description of method 900, specifically the description of 922 through 928.
FIGS. 9A-9C illustrate a flowchart representation of method 900 of fault prediction in a storage device, in accordance with some embodiments. In some embodiments, the storage device comprises a dual in-line memory module (DIMM) device. In some implementations, the storage device is compatible with a DIMM memory slot. For example, in some implementations, the storage device is compatible with a 240-pin DIMM memory slot using a DDR3 interface specification. In some implementations, the storage device comprises a storage controller (e.g., storage controller 120, FIG. 1) and a storage medium (e.g., storage medium 132, FIG. 1). In some implementations, the storage device coordinates and manages multiple sub-system components to detect faults, which initiates performance of method 900. At least in some implementations, method 900 is performed by a storage controller (e.g., storage controller 120, FIG. 1) or one or more components of the storage controller (e.g., management module 121 and/or current monitoring module 130, FIG. 1). In some embodiments, method 900 is governed by instructions that are stored in a non-transitory computer readable storage medium and that are executed by one or more processors of a device, such as the one or more processors 122 of management module 121, as shown in FIG. 1.
While in normal operation (902), the storage device records (904) data corresponding to electrical current drawn during performance of a respective operation on a specified portion of the storage device (e.g., by measuring electrical current drawn during performance of the respective operation on the specified portion of the storage device and recording data corresponding to the measured electrical current drawn during performance of the respective operation on the specified portion of the storage device). In some embodiments, the specified portion of the storage device includes, or is included in, one or more three-dimensional (3D) memory devices (e.g., memory device 212-1, FIG. 2). For additional details regarding this aspect of method 900 refer to the description of method 800, specifically the description of 802 and 804.
In some embodiments, the respective operation is completed (906) successfully. In some implementations, fault prediction is independent of whether the respective operation successfully completes. In some implementations, successful completion of the respective operation is a factor in determining whether predetermined warning criteria is met. In some implementations, failure of the respective operation to complete successfully meets predetermined failure criteria and, optionally, triggers one or more remedial actions.
In some embodiments, the recorded data corresponds to (908) a single scheduled operation, comprising the respective operation, performed by the storage device. For additional details regarding this aspect of method 900 refer to the description of method 800, specifically the description of 806.
In some embodiments, recording data corresponding to electrical current drawn during performance of the respective operation on the specified portion of the storage device comprises recording (910) a sequence of data corresponding to electrical current drawn during performance of the operation at a sequence of sample times. For additional details regarding this aspect of method 900 refer to the description of method 800, specifically the description of 808.
In some embodiments, the respective operation is selected (912) from a group consisting of: a read operation; an erase operation; and a write operation. For additional details regarding this aspect of method 900 refer to the description of method 800, specifically the description of 810.
The storage device analyzes (914) the recorded data, including determining whether one or more predefined characteristics of the recorded data meets predetermined warning criteria and does not meet predetermined failure criteria. In some implementations, meeting predetermined failure criteria indicates that the respective operation failed. In some implementations, meeting predetermined warning criteria indicates that, although the respective operation completed successfully, subsequent operations have an increased likelihood of failing. In some implementations, the predetermined warning criteria is stricter than the predetermined failure criteria such that recorded data that meets predetermined failure criteria always meets predetermined warning criteria as well.
In some embodiments, the one or more predefined characteristics of the recorded data comprises (916) at least one of: operation completion timing; cycle timing; peak current; floor current; average current; and difference current. For additional details regarding this aspect of method 900 refer to the description of method 800, specifically the description of 814.
In some embodiments, determining whether one or more predefined characteristics of the recorded data meets predetermined warning criteria comprises (918): generating a score based on the one or more predefined characteristics and a plurality of predetermined target values; and determining whether the generated score meets predetermined warning criteria. In some implementations, a predetermined target value is associated with each of the one or more predefined characteristics and the score is generated by adding the difference between each characteristic's recorded value and target value. If the generated score exceeds a predetermined limit then the score meets predetermined warning criteria. In some implementations, a particular weighting factor is associated with each predefined characteristic of the one or more predefined characteristics. For example, in some implementations, the generated score meets predetermined warning criteria if it exceeds 74. In this example, the generated score meets predetermined failure criteria if it exceeds 99.
In some embodiments, analyzing the recorded data includes (920) one or more of: determining a plurality of current peaks during the respective operation, determining one or more time intervals between said current peaks, and evaluating the time intervals in accordance with the predetermined warning criteria; identifying portions of the recorded data corresponding to each of a plurality of suboperations of the respective operation; for each of a subset of the plurality of suboperations, identifying current level and/or timing parameters, and evaluating the current level and/or timing parameters in accordance with the predetermined warning criteria; integrating at least a subset of the recorded sequence of data to generate a corresponding power measurement, and evaluating the generated power measurement in accordance with the predetermined warning criteria; evaluating average current drawn during at least a portion of the respective operation in accordance with the predetermined warning criteria; evaluating a completion time of the respective operation in accordance with the predetermined warning criteria; and evaluating a difference in current drawn during two distinct portions of the respective operation in accordance with the predetermined warning criteria. In some implementations, the predetermined warning criteria, optionally, includes warning criteria with respect to the one or more time intervals, suboperations, phases, and/or portions of the respective operation. For additional details regarding this aspect of method 900 refer to the description of method 800, specifically the description of 818.
In accordance with a determination that the recorded data meets the predetermined warning criteria and does not meet predetermined failure criteria, the storage device performs (922) one or more predictive actions. In some implementations, if the recorded data meets predetermined failure criteria then the storage device performs one or more remedial actions, regardless of whether or not the recorded data meets predetermined warning criteria. In some implementations, the one or more predictive actions comprise one or more of the remedial actions discussed previously with respect to method 800. In some implementations, the one or more predictive actions are coordinated by a management module (e.g., management module 121, FIG. 1).
In some embodiments, performing the one or more predictive actions comprises transferring (924) the data stored in the specified portion of the storage device to a second portion of the storage device. For example, the specified portion of the storage device is a memory block (e.g., memory devices block 134-1, FIG. 1) and transferring the data stored in the specified portion to a second portion comprises transferring the data to a second memory block (e.g., memory devices block 134-n, FIG. 1). In some implementations, one or more predictive actions comprises marking the specified portion of the storage device as a known-bad portion and transferring the data stored in the specified portion to a second portion of the storage device.
In some embodiments, performing the one or more predictive actions comprises updating (926) a mapping of the storage device to mark the specified portion as a known-bad portion. For example, mapping 600 in FIG. 6A indicates that portions 604-1 and 604-2 are known-bad portions. For additional details regarding this aspect of method 900 refer to the description of method 800, specifically the description of 820 and 822.
In some embodiments, performing the one or more predictive actions comprises updating (928) metadata corresponding to the specified portion of the storage device. In some implementations, the metadata corresponding to the specified portion of the storage device is stored in the specified portion. In some implementations, the metadata corresponding to the specified portion of the storage device is stored in volatile memory. In some implementations, the metadata corresponding to the specified portion of the storage device is stored in a second portion of the storage device. In some implementations, the metadata is first updated in volatile memory and then stored in non-volatile memory during a subsequent operation. In some implementations, the metadata corresponding to the specified portion of the storage device comprises metadata corresponding to subportions within the specified portion (e.g., metadata corresponding to blocks, pages, sectors, zones, and/or planes); and updating the metadata corresponding to the specified portion comprises updating the metadata corresponding to at least a subset of the subportions.
In some embodiments, updating the metadata includes flagging (930) the specified portion of the storage device for use with low priority data only. For example, in some implementations, low priority data is data that is duplicated elsewhere in the storage device. In some implementations, low priority data is data that can be reproduced if the specified portion fails and the data stored in it is lost and/or corrupted. In some implementations, low priority data is determined by a management module (e.g., management module 121, FIG. 1). In some implementations, low priority data is determined by a host system (e.g., computer system 110, FIG. 1).
In some embodiments, updating the metadata includes flagging (932) the specified portion of the storage device as being at risk of failing. In some implementations, portions flagged as being at risk of failing are fault checked more frequently than portions not flagged as being at risk of failing. For example, at risk portions are fault checked every 100 operations and portions not flagged as at risk are fault checked every 1000 operations. In some implementations, portions flagged as being at risk of failing used only for data of low importance (e.g., low priority data). In some implementations, portions flagged as being at risk of failing are used only for operations involving less dense amounts of data. For example, in some implementations, the specified portion comprises a plurality of memory devices (e.g., flash memory devices) and, after being flagged as at risk of failing, is excluded from use in operations that involve more than half of the plurality of device devices. In some implementations, portions marked as being at risk of failing are used only for operations involving small amounts of data.
In some embodiments, the storage device comprises (934) a plurality of distinct portions, where each portion in the plurality of distinct portions is assigned to a respective age category of a plurality of age categories; and performing one or more predictive actions comprises reassigning the specified portion of the storage device from a current age category to an older age category in the plurality of age categories. In some implementations, each portion in a storage medium (e.g., storage medium 132, FIG. 1) is assigned a respective age category. The age category is indicative of how many erase cycles remain before the risk of failure for the respective portion exceeds a predetermined threshold (e.g., 5%, 10%, 15%, etc.). For example, referring to FIG. 6B, the specified portion of the storage device is portion 1 and is initially assigned to age category 1 (e.g., the youngest age category) indicating the specified portion has approximately 3,000 erase cycles remaining In this example, performing one or more predictive actions comprises reassigning portion 1 to age category 4 indicating the specified portion has approximately 1,500 erase cycles remaining In some implementations, a portion that has failed one or more operations is reassigned to the oldest age category (e.g., age category 8, FIG. 6B) indicating that 0 erase cycles remaining In some implementations, a portion assigned to the oldest age category is a known-bad portion. In some implementations, the age categories assigned to the plurality of distinct portions are stored in a mapping (e.g., logical to physical mapping 722 in FIG. 7). In some implementations, the age category assigned to a particular portion is stored in metadata corresponding to the particular portion. In some implementations, a logical to physical mapping (e.g., logical to physical mapping 722 in FIG. 7) used by the storage device excludes portions of the storage device assigned to the oldest age category.
In some implementations, with respect to any of the methods described above, the storage device comprises a single NVM device (e.g., flash memory device), while in other implementations, the storage device includes a plurality of NVM devices (e.g., flash memory devices). In some implementations, with respect to any of the methods described above, the storage device comprises a storage controller (e.g., storage controller 120, FIG. 1) and a storage medium (e.g., storage medium 132, FIG. 1).
Semiconductor memory devices include volatile memory devices, such as dynamic random access memory (“DRAM”) or static random access memory (“SRAM”) devices, non-volatile memory devices, such as resistive random access memory (“ReRAM”), electrically erasable programmable read only memory (“EEPROM”), flash memory (which can also be considered a subset of EEPROM), ferroelectric random access memory (“FRAM”), and magnetoresistive random access memory (“MRAM”), and other semiconductor elements capable of storing information. Furthermore, each type of memory device may have different configurations. For example, flash memory devices may be configured in a NAND or a NOR configuration.
The memory devices can be formed from passive elements, active elements, or both. By way of non-limiting example, passive semiconductor memory elements include ReRAM device elements, which in some embodiments include a resistivity switching storage element, such as an anti-fuse, phase change material, etc., and optionally a steering element, such as a diode, etc. Further by way of non-limiting example, active semiconductor memory elements include EEPROM and flash memory device elements, which in some embodiments include elements containing a charge storage region, such as a floating gate, conductive nanoparticles or a charge storage dielectric material.
Multiple memory elements may be configured so that they are connected in series or such that each element is individually accessible. By way of non-limiting example, NAND devices contain memory elements (e.g., devices containing a charge storage region) connected in series. For example, a NAND memory array may be configured so that the array is composed of multiple strings of memory in which each string is composed of multiple memory elements sharing a single bit line and accessed as a group. In contrast, memory elements may be configured so that each element is individually accessible, e.g., a NOR memory array. One of skill in the art will recognize that the NAND and NOR memory configurations are exemplary, and memory elements may be otherwise configured.
The semiconductor memory elements included in a single device, such as memory elements located within and/or over the same substrate or in a single die, may be distributed in a two- or three-dimensional manner (such as a two dimensional (2D) memory array structure or a three dimensional (3D) memory array structure).
In a two dimensional memory structure, the semiconductor memory elements are arranged in a single plane or single memory device level. Typically, in a two dimensional memory structure, memory elements are located in a plane (e.g., in an x-z direction plane) which extends substantially parallel to a major surface of a substrate that supports the memory elements. The substrate may be a wafer on which the material layers of the memory elements are deposited and/or in which memory elements are formed or it may be a carrier substrate which is attached to the memory elements after they are formed. As a non-limiting example, the substrate may include a semiconductor such as silicon.
The memory elements may be arranged in the single memory device level in an ordered array, such as in a plurality of rows and/or columns. However, the memory elements may be arranged in non-regular or non-orthogonal configurations as understood by one of skill in the art. The memory elements may each have two or more electrodes or contact lines, including a bit line and a word line.
A three dimensional memory array is organized so that memory elements occupy multiple planes or multiple device levels, forming a structure in three dimensions (i.e., in the x, y and z directions, where the y direction is substantially perpendicular and the x and z directions are substantially parallel to the major surface of the substrate).
As a non-limiting example, each plane in a three dimensional memory array structure may be physically located in two dimensions (one memory level) with multiple two dimensional memory levels to form a three dimensional memory array structure. As another non-limiting example, a three dimensional memory array may be physically structured as multiple vertical columns (e.g., columns extending substantially perpendicular to the major surface of the substrate in the y direction) having multiple elements in each column and therefore having elements spanning several vertically stacked planes of memory devices. The columns may be arranged in a two dimensional configuration, e.g., in an x-z plane, thereby resulting in a three dimensional arrangement of memory elements. One of skill in the art will understand that other configurations of memory elements in three dimensions will also constitute a three dimensional memory array.
By way of non-limiting example, in a three dimensional NAND memory array, the memory elements may be connected together to form a NAND string within a single plane, sometimes called a horizontal (e.g., x-z) plane for ease of discussion. Alternatively, the memory elements may be connected together to extend through multiple parallel planes. Other three dimensional configurations can be envisioned wherein some NAND strings contain memory elements in a single plane of memory elements (sometimes called a memory level) while other strings contain memory elements which extend through multiple parallel planes (sometimes called parallel memory levels). Three dimensional memory arrays may also be designed in a NOR configuration and in a ReRAM configuration.
A monolithic three dimensional memory array is one in which multiple planes of memory elements (also called multiple memory levels) are formed above and/or within a single substrate, such as a semiconductor wafer, according to a sequence of manufacturing operations. In a monolithic 3D memory array, the material layers forming a respective memory level, such as the topmost memory level, are located on top of the material layers forming an underlying memory level, but on the same single substrate. In some implementations, adjacent memory levels of a monolithic 3D memory array optionally share at least one material layer, while in other implementations adjacent memory levels have intervening material layers separating them.
In contrast, two dimensional memory arrays may be formed separately and then integrated together to form a non-monolithic 3D memory device in a hybrid manner. For example, stacked memories have been constructed by forming 2D memory levels on separate substrates and integrating the formed 2D memory levels atop each other. The substrate of each 2D memory level may be thinned or removed prior to integrating it into a 3D memory device. As the individual memory levels are formed on separate substrates, the resulting 3D memory arrays are not monolithic three dimensional memory arrays.
Associated circuitry is typically required for proper operation of the memory elements and for proper communication with the memory elements. This associated circuitry may be on the same substrate as the memory array and/or on a separate substrate. As non-limiting examples, the memory devices may have driver circuitry and control circuitry used in the programming and reading of the memory elements.
Further, more than one memory array selected from 2D memory arrays and 3D memory arrays (monolithic or hybrid) may be formed separately and then packaged together to form a stacked-chip memory device. A stacked-chip memory device includes multiple planes or layers of memory devices, sometimes called memory levels.
The term “three-dimensional memory device” (or 3D memory device) is herein defined to mean a memory device having multiple layers or multiple levels (e.g., sometimes called multiple memory levels) of memory elements, including any of the following: a memory device having a monolithic or non-monolithic 3D memory array, some non-limiting examples of which are described above; or two or more 2D and/or 3D memory devices, packaged together to form a stacked-chip memory device, some non-limiting examples of which are described above.
A person skilled in the art will recognize that the invention or inventions descried and claimed herein are not limited to the two dimensional and three dimensional exemplary structures described here, and instead cover all relevant memory structures suitable for implementing the invention or inventions as described herein and as understood by one skilled in the art.
It will be understood that, although the terms “first,” “second,” etc. may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another. For example, a first record could be termed a second record, and, similarly, a record could be termed a first record, without changing the meaning of the description, so long as all occurrences of the “first record” are renamed consistently and all occurrences of the “second record” are renamed consistently. The first record and the second record are both records, but they are not the same record.
The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the claims. As used in the description of the embodiments and the appended claims, the singular forms “a,” “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will also be understood that the term “and/or” as used herein refers to and encompasses any and all possible combinations of one or more of the associated listed items. It will be further understood that the terms “comprises” and/or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.
As used herein, the term “if” may be construed to mean “when” or “upon” or “in response to determining” or “in accordance with a determination” or “in response to detecting,” that a stated condition precedent is true, depending on the context. Similarly, the phrase “if it is determined [that a stated condition precedent is true]” or “if [a stated condition precedent is true]” or “when [a stated condition precedent is true]” may be construed to mean “upon determining” or “in response to determining” or “in accordance with a determination” or “upon detecting” or “in response to detecting” that the stated condition precedent is true, depending on the context.
The foregoing description, for purpose of explanation, has been described with reference to specific embodiments. However, the illustrative discussions above are not intended to be exhaustive or to limit the claims to the precise forms disclosed. Many modifications and variations are possible in view of the above teachings. The embodiments were chosen and described in order to best explain principles of operation and practical applications, to thereby enable others skilled in the art.

## Claims

1. A method of fault detection in a storage device, the method comprising:
while in normal operation:
measuring electrical current drawn during performance of a respective operation on a specified portion of the storage device and recording data corresponding to the measured electrical current drawn during performance of the respective operation on the specified portion of the storage device;
analyzing the recorded data, including determining whether one or more predefined characteristics of the recorded data meets predetermined failure criteria; and
in accordance with a determination that the recorded data meets the predetermined failure criteria, performing one or more remedial actions, the one or more remedial actions including marking the specified portion of the storage device as a known-bad portion.

2. The method of claim 1, wherein marking the specified portion of the storage device as the known-bad portion includes updating a mapping table of the storage device to indicate that the specified portion of the storage device should not be used.

3. The method of claim 1, wherein performing the one or more remedial actions comprises:
determining whether the respective operation completed; and
in accordance with a determination that the respective operation did not complete, aborting the respective operation.

4. The method of claim 1, wherein performing the one or more remedial actions comprises:
determining whether data stored in the specified portion of the storage device is valid; and
in accordance with a determination that the data stored in the specified portion is valid, transferring the data stored in the specified portion of the storage device to a second portion of the storage device.

5. The method of claim 4, further comprising, in accordance with a determination that the data stored in the specified portion is invalid, obtaining recovered data corresponding to the data stored in the specified portion of the storage device and storing the recovered data to a second portion of the storage device.

6. The method of claim 1, wherein the recorded data corresponds to a single scheduled operation, comprising the respective operation, performed by the storage device.

7. The method of claim 1, wherein recording data corresponding to electrical current drawn during performance of the respective operation on the specified portion of the storage device comprises recording a sequence of data corresponding to electrical current drawn during performance of the operation at a sequence of sample times.

8. The method of claim 7, wherein analyzing the recorded data includes one or more of:
determining a plurality of current peaks during the respective operation, determining one or more time intervals between said current peaks, and evaluating the time intervals in accordance with the predetermined failure criteria;
identifying portions of the recorded data corresponding to each of a plurality of suboperations of the respective operation; for each of a subset of the plurality of suboperations, identifying current level and/or timing parameters, and evaluating the current level and/or timing parameters in accordance with the predetermined failure criteria;
integrating at least a subset of the recorded sequence of data to generate a corresponding power measurement, and evaluating the generated power measurement in accordance with the predetermined failure criteria;
evaluating average current drawn during at least a portion of the respective operation in accordance with the predetermined failure criteria;
evaluating a completion time of the respective operation in accordance with the predetermined failure criteria; and
evaluating a difference in current drawn during two distinct portions of the respective operation in accordance with the predetermined failure criteria.

9. The method of claim 1, wherein the one or more predefined characteristics of the recorded data comprises at least one of:
operation completion timing;
cycle timing;
peak current;
floor current;
average current; and
difference current.

10. The method of claim 1, wherein determining whether one or more predefined characteristics of the recorded data meets the predetermined failure criteria comprises:
generating a score based on the one or more predefined characteristics and a plurality of predetermined target values; and
determining whether the generated score meets predetermined failure criteria.

11. The method of claim 1, wherein the respective operation is selected from a group consisting of:
a read operation;
an erase operation; and
a write operation.

12. The method of claim 1, further comprising:
in accordance with a determination that the recorded data does not meet the predetermined failure criteria, determining whether the one or more predefined characteristics of the recorded data meets predetermined warning criteria;
in accordance with a determination that the recorded data meets the predetermined warning criteria, performing one or more predictive actions.

13. A storage device, comprising:
a storage medium;
a storage controller coupled to the storage medium, the storage controller including:
one or more processors;
an interface for coupling the storage controller to the storage medium; and
a current monitoring module, the current monitoring module configured to perform one or more operations including:
while in normal operation:
measuring electrical current drawn during performance of a respective operation on a specified portion of the storage device and recording data corresponding to the measured electrical current drawn during performance of the respective operation on the specified portion of the storage device;
analyzing the recorded data, including determining whether one or more predefined characteristics of the recorded data meets predetermined failure criteria; and
in accordance with a determination that the recorded data meets the predetermined failure criteria, performing one or more remedial actions, the one or more remedial actions including marking the specified portion of the storage device as a known-bad portion.

14. The storage device of claim 13, wherein marking the specified portion of the storage device as the known-bad portion includes:
updating a mapping table of the storage device to indicate that the specified portion of the storage device should not be used.

15. The storage device of claim 13, wherein performing the one or more remedial actions comprises:
determining whether data stored in the specified portion of the storage device is valid; and
in accordance with a determination that the data stored in the specified portion is valid, transferring the data stored in the specified portion of the storage device to a second portion of the storage device.

16. The storage device of claim 15, wherein the current monitoring module is further configured to obtain recovered data corresponding to the data stored in the specified portion of the storage device and store the recovered data to a second portion of the storage device in accordance with a determination that the data stored in the specified portion is invalid.

17. The storage device of claim 13, wherein recording data corresponding to electrical current drawn during performance of the respective operation on the specified portion of the storage device comprises:
recording a sequence of data corresponding to electrical current drawn during performance of the operation at a sequence of sample times.

18. The storage device of claim 17, wherein analyzing the recorded data includes one or more of:
determining a plurality of current peaks during the respective operation, determining one or more time intervals between said current peaks, and evaluating the time intervals in accordance with the predetermined failure criteria;
identifying portions of the recorded data corresponding to each of a plurality of suboperations of the respective operation; for each of a subset of the plurality of suboperations, identifying current level and/or timing parameters, and evaluating the current level and/or timing parameters in accordance with the predetermined failure criteria;
integrating at least a subset of the recorded sequence of data to generate a corresponding power measurement, and evaluating the generated power measurement in accordance with the predetermined failure criteria;
evaluating average current drawn during at least a portion of the respective operation in accordance with the predetermined failure criteria;
evaluating a completion time of the respective operation in accordance with the predetermined failure criteria; and
evaluating a difference in current drawn during two distinct portions of the respective operation in accordance with the predetermined failure criteria.

19. The storage device of claim 13, wherein determining whether one or more predefined characteristics of the recorded data meets the predetermined failure criteria comprises:
generating a score based on the one or more predefined characteristics and a plurality of predetermined target values; and
determining whether the generated score meets predetermined failure criteria.

20. A non-transitory computer readable storage medium, storing one or more programs for execution by one or more processors of a storage device, the one or more programs including instructions for:
while in normal operation:
measuring electrical current drawn during performance of a respective operation on a specified portion of the storage device and recording data corresponding to the measured electrical current drawn during performance of the respective operation on the specified portion of the storage device;
analyzing the recorded data, including determining whether one or more predefined characteristics of the recorded data meets predetermined failure criteria; and
in accordance with a determination that the recorded data meets the predetermined failure criteria, performing one or more remedial actions, the one or more remedial actions including marking the specified portion of the storage device as a known-bad portion.

21. The non-transitory computer readable storage medium of claim 20, wherein marking the specified portion of the storage device as the known-bad portion includes:
updating a mapping table of the storage device to indicate that the specified portion of the storage device should not be used.

22. The non-transitory computer readable storage medium of claim 20, wherein performing the one or more remedial actions comprises:
determining whether data stored in the specified portion of the storage device is valid; and
in accordance with a determination that the data stored in the specified portion is valid, transferring the data stored in the specified portion of the storage device to a second portion of the storage device.

23. The non-transitory computer readable storage medium of claim 20, wherein recording data corresponding to electrical current drawn during performance of the respective operation on the specified portion of the storage device comprises:
recording a sequence of data corresponding to electrical current drawn during performance of the operation at a sequence of sample times.

24. The non-transitory computer readable storage medium of claim 23, wherein analyzing the recorded data includes one or more of:
determining a plurality of current peaks during the respective operation, determining one or more time intervals between said current peaks, and evaluating the time intervals in accordance with the predetermined failure criteria;
identifying portions of the recorded data corresponding to each of a plurality of suboperations of the respective operation; for each of a subset of the plurality of suboperations, identifying current level and/or timing parameters, and evaluating the current level and/or timing parameters in accordance with the predetermined failure criteria;
integrating at least a subset of the recorded sequence of data to generate a corresponding power measurement, and evaluating the generated power measurement in accordance with the predetermined failure criteria;
evaluating average current drawn during at least a portion of the respective operation in accordance with the predetermined failure criteria;
evaluating a completion time of the respective operation in accordance with the predetermined failure criteria; and
evaluating a difference in current drawn during two distinct portions of the respective operation in accordance with the predetermined failure criteria.

25. The non-transitory computer readable storage medium of claim 20, wherein determining whether one or more predefined characteristics of the recorded data meets predetermined failure criteria comprises:
generating a score based on the one or more predefined characteristics and a plurality of predetermined target values; and
determining whether the generated score meets predetermined failure criteria.