Patent Publication Number: US-2023133278-A1

Title: Removable solid state storage system with data loss prevention and user alert

Description:
TECHNICAL FIELD 
     The disclosure herein relates to data loss prevention for solid state storage devices, particularly relates to data loss prevention for removable solid state storage devices. 
     BACKGROUND 
     The evolution of the modern computing system is driven in-part by the emergence of the solid state drives (SSD) that have demonstrated higher performance of speed and latency over the traditional hard drives. Unlike hard drives that depend on the magnetism to store data, solid state drives use NAND flash devices to achieve data storage. The NAND flash devices are a family of integrated circuits that are manufactured by advanced process and assembly technologies to achieve multiple levels of  3 D vertical stacking of storages units into a small footprint of die and package for high capacity of storage. 
     Meanwhile, the increased storage capacity with new NAND flash process technology evolutions such as triple-level cell (TLC) and quadruple-level cell (QLC) has also introduced new challenges of reduced reliability and decreased data retention time. For example, for QLC NAND flash devices, the data retention time usually ranges from two to three months, which makes it mandatory for the firmware to refresh NAND storage blocks every 30 to 60 days to prevent data loss. 
     The removable solid state drives are expected to be disconnected from the power supply for a long period of time from months to years without any data loss. Without power supply, a removable solid state drive is unable to perform NAND refresh to prolong the data retention time. As a result, a removable solid state drive with QLC NAND flash devices will end up losing data after a few months of being disconnected from the USB power supply. Therefore, data loss issue has limited mass adoption of removable solid state drives. 
     SUMMARY 
     The present disclosure provides a novel removable solid state storage system and method with data loss prevention and user alert functions. The system may include a timer, a wireless module and a removable battery in a removable solid state drive. The removable battery may provide dedicated power supply to the removable solid state drive to perform NAND storage refresh at a time interval set by the timer. The method may include data refresh back-up schemes and a user alert scheme to suggest action items to the user for preventing potential data loss. 
     In one exemplary embodiment, there is provided an apparatus that may comprise an external connection interface, a timer, a removable battery, one or more non-volatile memory devices and a storage controller. The timer may be configured to maintain a standby mode when the external connection interface is connected to an external power supply, set an operation time interval, count how long the external connection interface has been disconnected, and send an interrupt to the storage controller when the timer counts to the operation time Interval. The storage controller may be coupled to the timer, the removable battery and the one or more non-volatile memory devices, and configured to activate upon receipt of the interrupt, and perform data loss prevention operations on data stored in the one or more non-volatile memory devices using a power supplied by the removable battery. 
     In another exemplary embodiment, there is provided a method for managing a removable solid state storage system for data loss prevention. The method may comprise: maintaining a standby mode for a timer of the removable solid state storage system until the removable solid state storage system is disconnected from an external power supply, setting an operation time interval on the timer, using the timer to count how long the removable solid state storage system has been disconnected, sending an interrupt to a storage controller of the removable solid state storage system from the timer when the timer counts to the operation time Interval, and performing data loss prevention operations using a power supplied by a removable battery. 
    
    
     
       BRIEF DESCRIPTION OF FIGURES 
         FIG.  1    schematically shows a removable solid state storage system in accordance with an embodiment of the present disclosure. 
         FIG.  2    is a flowchart of a process for conducting data loss prevention of a removable solid state storage system in accordance with an embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Specific embodiments according to the present disclosure will now be described in detail with reference to the accompanying figures. Like elements in the various figures are denoted by like reference numerals for consistency. 
     The present disclosure provides systems and methods for preventing data loss in non-volatile memory device based storage systems. As used herein, a non-volatile memory device may be a computer storage device that can maintain stored information after being powered off, and the stored information may be retrieved after being power cycled (turned off and back on). Non-volatile storage memory devices may include NAND flash memories, NOR flash memories, magnetoresistive random Access Memory (MRAM), resistive random access memory (RRAM), phase change random access memory (PCRAM), Nano-RAM, etc. In the description, a NAND flash may be used as an example to demonstrate data loss prevention techniques. However, various embodiments according to the present disclosure may implement the techniques with other types of non-volatile storage devices. 
       FIG.  1    schematically shows a removable solid state storage system  100  in accordance with an embodiment of the present disclosure. The removable solid state storage system  100  may comprise a storage controller  102 , an external connection interface  104 , a wireless module  106 , a timer  108 , a removable battery  110 , a voltage regulator  114  and one or more non-volatile memory (NVM) devices  112 . In one embodiment, the removable solid state storage system  100  may be a removable solid state drive (SSD) or a portable SSD. 
     The NVM devices  112  may provide non-volatile data storage for the removable solid state storage system  100 . In some embodiments, the NVM devices  112  may be one or more NAND flash devices. In some other embodiments, the NVM devices  112  may be one or more other types of non-volatile storage devices, for example, NOR flash memories, magnetoresistive random Access Memory (MRAM), resistive random access memory (RRAM), phase change random access memory (PCRAM), Nano-RAM, etc. 
     The external connection interface  104  may be part of the removable solid state storage system  100  to connect the removable solid state storage system  100  to a host system, which also provides an external power supply to the removable solid state system. For example, the external connection interface  104  may be a PCIe to USB bridge for connecting the removable solid state storage system  100  to a USB port of a host system. The voltage regulator  114  may be configured to adapt the power provided by a power source (e.g., the removable battery  110  or a USB connection) for circuits of the removable solid state storage system  100 . In some embodiments, the removable solid state storage system  100  may have more than one voltage regulator. 
     The storage controller  102  may be configured to control and manage the NVM devices  112  and other components of the removable solid state storage system  100 . In some embodiments, the storage controller  102  may implement functionalities of a solid state drive (SSD) controller, and also data loss prevention operations. The data loss prevention operations may include data retention operations and user notifications, and the data retention operations may further include data refresh and data back-up operations. In at least one embodiment, the removable solid state storage system  100  may include firmware that includes executable instructions to manage the removable solid state storage system  100 . For example, the storage controller  102  may comprise a computer processor (e.g., a microprocessor or a microcontroller) configured to execute the executable instructions of the firmware to perform various operations for managing data in the NVM devices  112  (e.g., regular operations of an SSD controller and data loss prevention operations). 
     The wireless module  106  may connect the removable solid state storage system  100  to a user device and perform user alert functions under the control of the storage controller  102 . In one example embodiment, the wireless module may be a WiFi controller, or a Bluetooth controller, and a combination of both WiFi and Bluetooth controllers. The timer  108  and the removable battery  110  may be used to perform data refresh and back-up operations under the control of the storage controller  102  when the removable solid state storage system  100  is disconnected from an external power supply (e.g., a host system). 
     The timer  108  may manage the time intervals between successive data retention and user alert operations. The time intervals may also be referred to as operation time intervals. In an embodiment, the timer  108  may remain at a standby mode while removable solid state storage system  100  may be connected to an external power supply (e.g., a USB port) and may be turned on (e.g., start counting time) once the removable solid state storage system  100  is disconnected from the power supply. The timer  108  may stay on (e.g., keep counting) while the removable solid state storage system  100  is disconnected and send an interrupt signal to the storage controller  102  once the end of a pre-set time interval has reached (or end of the time interval depending on whether the timer counts from zero to the time interval or from the time interval to zero). The interrupt may activate the storage controller  102  to perform the data retention operations. 
     While the interrupt is asserted to the storage controller  102 , the timer  108  may be reset and re-start counting time again. Another interrupt may be sent to the storage controller  102  after the counted time reaches the time interval again. The operations of re-starting to count time and sending an interrupt may be repeated as long as the removable solid state storage system  100  is disconnected from any external power supply. 
     The time interval between successive data retention operations may depend on a variety of factors that represent the reliability and retention time of the solid state storage device  104 . These factors may include the device type such as triple-level cell (TLC) or quadruple-level cell (QLC), the program/erase (P/E) cycle counts, the page error count and the program time. In one embodiment, the time interval for QLC NAND flash devices may be set around 30 to 60 days, while for TLC it may be a few years. A large P/E cycle count or page error count may be indicators that a solid state storage device may have entered the late stage of its lifetime, and thus a smaller interval between data loss prevention operations may be needed to ensure data retention. 
     In some embodiments, the removable battery  110  may provide a dedicated power supply to the removable solid state storage system  100  for the data loss prevention operations. The battery may be designed to be removable so that the user has the convenient option to replace it. In one embodiment, the battery level of the removable battery  110  may also be reported to the storage controller  102  and reported to a user via the wireless module  106 , such that the user may be notified in a timely manner of further necessary actions or pending risks. 
     The backup battery  110  may be recharged in place, or recharged after being removed. In one example embodiment, the removable battery  110  may be a button cell battery with nominal voltage of 3V to 3.3V. In another example embodiment, the removable battery  110  may be rechargeable while the removable solid state storage system  100  is connected to an external power supply. 
     In various embodiments, the data loss prevention operations may include data refresh and data back-up. In some embodiments, the removable solid state storage system  100  may also be configured to send notifications via the wireless module  106  to a user (e.g., by wireless connections such as Bluetooth, 3G/4G/5G or other wireless technology) using Simple Text Message (SMS), E-mail or mobile application in-app messages. In such embodiments, in addition to data refresh and back-up, the data loss prevention operations may also include user notifications. 
     In a data refresh operation, the storage controller  102  may read data from the one or more NVM devices  112 , correct errors through controller&#39;s ECC schemes and re-program the data into the NVM devices  112 . In a data back-up operation, in contrast, the storage controller  102  may read data from the one or more NVM devices  112 , correct errors through controller&#39;s ECC schemes and program the data to a second location of the NVM devices  112 . As a result, a second copy of the data may be retained at a different physical block after a back-up operation. In some embodiments, for the data retention operations, the storage controller  102  may be configured (e.g., by firmware) to prioritize and selectively back-up data for the operating system, critical programs and important user data. 
     In embodiments that provide user notifications, the user notification operations may be performed at the same or different intervals as the refresh and back-up operations. Exemplary notifications may include the battery level of the backup battery  110 , and one or more suggested action items, such as, but not limited to, connecting the removable solid state storage system  100  to an external power supply or replacing the removable battery  110  to prevent potential data loss. 
       FIG.  2    is a flowchart of a process  200  for conducting data loss prevention of a removable solid state storage system in accordance with an embodiment of the present disclosure. At block  202 , a timer of a removable solid state storage system may be maintained at a standby mode until the removable solid state storage system is disconnected from an external power supply. For example, as long as the removable solid state storage system  100  is connected to an external power supply, such as a USB port of a host system, the timer  108  of the removable solid state storage system  100  may be kept at a standby mode. 
     At block  204 , an operation time interval may be set for the timer. For example, the timer  108  may be set with an operation time interval. In some embodiments, the operation time interval may be pre-configured and set before the removable solid state storage system  100  is disconnected from an external power supply. In some other embodiments, the operation time interval may be set when the removable solid state storage system  100  is disconnected from an external power supply. 
     At block  206 , the timer may be started to count how long the removable solid state storage system has been disconnected from the external power supply. For example, the timer  108  may start to count once the removable solid state storage system is unplugged from an external power supply. In some embodiments, the timer  108  may count up (e.g., from zero counting towards the time interval). In some other embodiments, the timer  108  may count down (e.g., from the time interval counting towards zero). 
     At block  208 , an interrupt may be sent to a storage controller from the timer when the timer counts to the operation time interval. For example, when the timer  108  counts to the value of the operation time interval, an interrupt may be generated by the timer  108  and sent to the storage controller  102 . At block  210 , data loss prevention operations may be performed using power supplied by a removable battery. In some embodiments, the data loss prevention operations may include data refresh and back-up operations to be performed by the storage controller  102  for data stored in the NVMs  112 . In at least one embodiment, the data loss prevention operations may further include issuing user notifications (e.g., SMS, email, and/or mobile app messages). 
     In some embodiments, when the timer finishes counting for one operation time interval, the timer may then continue counting towards the next operation cycle. For example, the timer  108  may start counting again for the next operation cycle after the interrupt has been sent or the data loss prevention operations have been performed. And the data loss prevention operations may be performed again after another operation time interval. 
     In some embodiments, once the removable solid state storage system is connected to an external power supply in the middle of any time interval, the timer may be sent back to the standby mode and stop counting. 
     In one exemplary embodiment, there is provided an apparatus that may comprise an external connection interface, a timer, a removable battery, one or more non-volatile memory devices and a storage controller. The timer may be configured to maintain a standby mode when the external connection interface is connected to an external power supply, set an operation time interval, count how long the external connection interface has been disconnected, and send an interrupt to the storage controller when the timer counts to the operation time Interval. The storage controller may be coupled to the timer, the removable battery and the one or more non-volatile memory devices, and configured to activate upon receipt of the interrupt, and perform data loss prevention operations on data stored in the one or more non-volatile memory devices using a power supplied by the removable battery. 
     In one embodiment, the data loss prevention operations may include refresh and back-up the data stored in the one or more non-volatile memory devices. 
     In one embodiment, the apparatus may further comprise a wireless module, and the data loss prevention operations may further include sending one or more user notifications via the wireless module. 
     In one embodiment, for the data loss prevention operations, the storage controller may be further configured to prioritize and selectively back-up the data stored in the one or more non-volatile memory devices for an operating system, critical programs and important user data. 
     In one embodiment, the storage controller may be further configured to use the timer to count how much time has passed since the data loss prevention operations have been performed and use another interrupt from the timer to activate the storage controller to repeat the data loss prevention operations. 
     In one embodiment, the removable battery may be a rechargeable battery and recharged when the external connection interface is connected to any external power supply. 
     In one embodiment, the removable battery may be a button cell battery with nominal voltage of 3V to 3.3V. 
     In one embodiment, the operation time interval may be determined based on a variety of factors that represent a reliability and retention time of the one or more non-volatile memory devices. 
     In one embodiment, when the removable solid state storage system may be connected to another external power supply in the middle of any time interval, the timer is sent back to the standby mode and stops counting. 
     In one embodiment, the external connection interface may be a PCIe to USB bridge. 
     In another exemplary embodiment, there is provided a method for managing a removable solid state storage system for data loss prevention. The method may comprise: maintaining a standby mode for a timer of the removable solid state storage system until the removable solid state storage system is disconnected from an external power supply, setting an operation time interval on the timer, using the timer to count how long the removable solid state storage system has been disconnected, sending an interrupt to a storage controller of the removable solid state storage system from the timer when the timer counts to the operation time Interval, and performing data loss prevention operations using a power supplied by a removable battery. 
     In one embodiment, the data loss prevention operations may include refresh and back-up data stored in one or more non-volatile memory devices of the removable solid state storage system. 
     In one embodiment, the data loss prevention operations may further include sending one or more user notifications. 
     In one embodiment, for the data loss prevention operations, the storage controller may be configured to prioritize and selectively back-up data for an operating system, critical programs and important user data. 
     In one embodiment, the method may further comprise using the timer to count how much time has passed since the data loss prevention operations have been performed and sending another interrupt to activate the storage controller to repeat the data loss prevention operations. 
     In one embodiment, the removable battery may be a rechargeable battery and recharged when the removable solid state storage system is connected to any external power supply. 
     In one embodiment, the removable battery may be a button cell battery with nominal voltage of 3V to 3.3V. 
     In one embodiment, the operation time interval may be determined based on a variety of factors that represent a reliability and retention time of the one or more non-volatile memory devices. 
     In one embodiment, the method may further comprise sending the timer back to the standby mode and stopping counting when the removable solid state storage system is connected to any external power supply in the middle of any time interval. 
     In one embodiment, the removable solid state storage system may be connected to the external power supply via a PCIe to USB bridge. 
     Any of the disclosed methods and operations may be implemented as computer-executable instructions (e.g., software code for the operations described herein) stored on one or more computer-readable storage media (e.g., non-transitory computer-readable media, such as one or more optical media discs, volatile memory components (such as DRAM or SRAM), or nonvolatile memory components (such as hard drives)) and executed on a device controller (e.g., firmware executed by ASIC). Any of the computer-executable instructions for implementing the disclosed techniques as well as any data created and used during implementation of the disclosed embodiments can be stored on one or more computer-readable media (e.g., non-transitory computer-readable media). 
     While various aspects and embodiments have been disclosed herein, other aspects and embodiments will be apparent to those skilled in the art. The various aspects and embodiments disclosed herein are for purposes of illustration and are not intended to be limiting, with the true scope and spirit being indicated by the following claims.