Virtual Memory Device (VMD) Application/Driver with Dual-Level Interception for Data-Type Splitting, Meta-Page Grouping, and Diversion of Temp Files to Ramdisks for Enhanced Flash Endurance

• US 20130145085A1
• Filed: 12/28/2012
• Published: 06/06/2013
• Est. Priority Date: 06/18/2008
• Status: Active Grant

• Current Assignee: Super Talent Technology, Corporation
• Original Assignee: Super Talent Technology, Corporation
• Inventors: Yu, Frank, Ma, Abraham C., Chen, Shimon, Yan, Yi Syu
• Granted Patent: US 8,954,654 B2
• Time in Patent Office: Days
• US Class Current: 711/103
• CPC Class Codes: G06F 12/0246 in block erasable memory, e.g. flash memory
• CPC Class Codes: G06F 12/0804 with main memory updating G06F12/0806 takes precedence
• CPC Class Codes: G06F 12/0871 Allocation or management of cache space
• CPC Class Codes: G06F 2212/401 Compressed data
• CPC Class Codes: G06F 2212/402 Encrypted data
• CPC Class Codes: G06F 2212/7203 Temporary buffering, e.g. using volatile buffer or dedicated buffer blocks
• CPC Class Codes: G06F 2212/7208 Multiple device management, e.g. distributing data over multiple flash devices
• CPC Class Codes: G06F 3/0616 in relation to life time, e.g. increasing Mean Time Between Failures [MTBF]
• CPC Class Codes: G06F 3/0644 Management of space entities, e.g. partitions, extents, pools
• CPC Class Codes: G06F 3/0659 Command handling arrangements, e.g. command buffers, queues, command scheduling
• CPC Class Codes: G06F 3/0679 Non-volatile semiconductor memory device, e.g. flash memory, one time programmable memory [OTP]
• CPC Class Codes: G11C 13/0004 comprising amorphous/crystalline phase transition cells
• CPC Class Codes: G11C 16/349 Arrangements for evaluating degradation, retention or wearout, e.g. by counting erase cycles
• CPC Class Codes: G11C 29/765 in solid state disks

Abstract

A Virtual-Memory Device (VMD) driver and application execute on a host to increase endurance of flash memory attached to a Super Enhanced Endurance Device (SEED) or Solid-State Drive (SSD). Host accesses to flash are intercepted by the VMD driver using upper and lower-level filter drivers and categorized as data types of paging files, temporary files, meta-data, and user data files, using address ranges and file extensions read from meta-data tables. Paging files and temporary files are optionally written to flash. Full-page and partial-page data are grouped into multi-page meta-pages by data type before storage by the SSD. ramdisks and caches for storing each data type in the host DRAM are managed and flushed to the SSD by the VMD driver. Write dates are stored for pages or blocks for management functions. A spare/swap area in DRAM reduces flash wear. Reference voltages are adjusted when error correction fails.

Claims

1. A Virtual-Memory Device (VMD) driver for executing on a host comprising:

a file type identifier for generating a data type for a host write received by the VMD driver;

a data split manager for sorting host write data based on the data type generated by the file type identifier;

a data write cache for storing host write data having a user data type;

a meta-data cache for storing host write data having a meta-data data type;

a paging cache for storing host write data having a paging file data type;

a temp cache for storing host write data having a temp data type;

a user grouping engine for grouping user data stored in the data write cache into user meta-pages;

a meta-data grouping engine for grouping meta-data data stored in the data write cache into meta-data meta-pages; and

an output buffer for sending grouped meta-pages and data type information to a flash drive system for storage.

2. The VMD driver of claim 1 further comprising:

an upper-level file filter driver, for executing on the host, for intercepting high-level host writes to a flash drive;

an encryption engine, coupled to receive high-level host writes intercepted by the upper-level file filter driver, for generating encrypted data;

a compression engine, coupled to receive high-level host writes from the upper-level file filter driver, for generating compressed data;

wherein compressed data and encrypted data are sent to a file system driver executing on the host; and

a lower-level file filter driver, for executing on the host, for intercepting lower-level file system host writes to the flash drive and sending the lower-level file system host writes to the data split manager for sorting as the host write data.

3. The VMD driver of claim 1 further comprising:

a ramdisk driver for storing data in the temp cache or data in a browser cache or data in an application program cache to a ramdisk stored in a host dynamic-random-access memory (DRAM).

4. The VMD driver of claim 1 further comprising:

a first data read cache for storing frequently-accessed, recently-accessed data for reading by the host;

a second data read cache for storing frequently-accessed, non-recently-accessed data for reading by the host;

a third data read cache for storing non-frequently-accessed, recently-accessed data for reading by the host;

a fourth data read cache for storing non-frequently-accessed, non-recently-accessed data for reading by the host;

a first split manager for splitting data received from the flash drive system into recently-accessed and non-recently-accessed data; and

a second split manager for splitting data received from the flash drive system into frequently-accessed and non-frequently-accessed data.

5. The VMD driver of claim 1 wherein the flash drive system is a Super Enhanced Endurance Device (SEED) which comprises:

a Solid-State Drive (SSD) Endurance Translation Layer (ETL) implemented in the DRAM and controlled by a controller that uses the ETL to provide temporary storage to reduce flash wear;

a Solid-State Drive (SSD) DRAM buffer for storing the grouped meta-pages;

a DRAM interface for accessing the SSD DRAM buffer;

an error-correction code (ECC) manager for generating ECC code to append to the grouped meta-pages written to the flash memory;

a bad page manager for tracking bad pages of the flash memory;

a wear leveler for assigning new data to empty blocks of the flash memory having a low erase count;

a flash interface for erasing blocks and writing pages in the flash memory, wherein a block is a multiple of pages in size; and

a flash memory for storing grouped meta-pages from the SSD DRAM buffer.

6. A Virtual-Memory Device (VMD) driver for executing on a host comprising:

a data type assignor for generating a data type for a host write received by the VMD driver;

a task priority assignor for assigning a priority to tasks including writing of host write data by data type, wherein priority is a function of the data type from the data type assignor;

a target assignor for sorting host write data based on the data type generated by the data type assignor;

a data write cache for storing host write data having a user data type;

a ramdisk driver for storing host write data having a temp data type to a ramdisk stored in a host dynamic-random-access memory (DRAM);

a data read cache for storing data for reading by the host;

a grouping engine for grouping data stored in the data write cache into meta-pages;

an un-grouping engine for un-grouping data in stored in meta-pages into ungrouped data for storage in the data read cache;

wherein meta-pages are sent from the grouping engine to a volume manager for transfer to a flash memory, and meta-pages stored in the flash memory are received by the un-grouping engine;

a power monitor for detecting a power failure;

a flush manager for flushing data stored in the host DRAM to a SSD DRAM and then to a flash memory of a flash drive system when power is lost;

a resume manager reloader for fetching flushed data from flash memory of the flash drive system and then to the host DRAM when power is restored.

7. The VMD driver of claim 6 further comprising:

a transaction manager for logging events indicating start and completion of data writes to the flash memory; and

a recovery manager for reading events logged by the transaction manager to undo or redo writes to the flash memory after power resumes.

8. The VMD driver of claim 6 further comprising:

a configuration settings manager for disabling settings to improve flash endurance, the settings comprising at least one of drive indexing, search indexing, defragmentation, host hibernation, prefetching, superfetching, write caching, and write cache buffer flushing.

9. A method for refreshing a flash memory comprising:

obtaining a current date;

for a current block in a list of blocks in the flash memory;

(a) reading a block status table for an erase count of the current block and for a write date of the current block that indicates when the current block was last written;

calculating a first time delay as a difference of the write date and the current date;

comparing the first time delay to a retention time;

when the first time delay exceeds the retention time, moving all valid pages in the current block to empty pages in a spare block in a dynamic-random-access memory (DRAM);

when the spare block in the DRAM is full, moving data from the spare block in DRAM to a spare block in the flash memory;

erasing the current block;

selecting another block in the list of blocks of flash memory as the current block and repeating from (a) until all blocks in the list of blocks have been processed,

whereby flash blocks are refreshed.

10. A method for refreshing a flash memory comprising:

obtaining a current date;

for a current page in a current block in a list of blocks in the flash memory;

(a) reading a block status table for an erase count of the current block;

(b) reading a page status table for a write date of the current page that indicates when the current page was last written;

calculating a first time delay as a difference of the write date and the current date;

comparing the first time delay to a retention time;

when the first time delay exceeds the retention time, moving the current page in the current block to an empty page in a spare block in a dynamic-random-access memory (DRAM), and marking the current page as garbage page;

when the spare block in the DRAM is full, moving data from the spare block in DRAM to a spare block in the flash memory;

selecting another page in the current block and repeating from (b) until all pages in the current block have been processed;

selecting another block in the list of blocks of flash memory as the current block and repeating from (a) until all blocks in the list of blocks have been processed,

whereby flash pages are refreshed.

11. The method of claim 10 further comprising:

calculating the retention time as a function of the erase count of the current block.

12. A Super Enhanced Endurance Device (SEED) Solid-State Drive (SSD) Endurance Translation Layer (ETL) method to increase endurance of a flash memory having a low specified erase-cycle lifetime comprising:

creating an ETL in a dynamic-random-access memory (DRAM) buffer that is controlled by a controller and using the ETL to provide temporary storage to reduce flash wear;

creating a spare/swap area in the DRAM buffer;

operating a controller to use the spare/swap area in the DRAM buffer to merge valid data in a flash memory with new data to generate combined data;

when over-writing a full page or a partial page of an existing block in the flash memory, writing new data to a spare block in the DRAM buffer related to the existing block in the flash memory, and when the spare block is needed by additional new data for a different block in the flash memory, writing a combination of the spare block with the new data and data from the existing block in the flash memory into a swap block in the flash memory and marking a page status as a garbage page for all pages of the existing block in the flash memory; and

using a backup power supply to power the DRAM buffer and the flash memory and the controller when power is lost, the backup power supply having a sufficient capacity for the controller to copy desired data in the ETL to the flash memory,

whereby a spare/swap function is performed by the controller using the DRAM buffer rather than the flash memory.

13. A Super Enhanced Endurance Device (SEED) comprising:

a host interface for receiving host reads and host writes from a host;

a SEED dynamic-random-access memory (DRAM) buffer for storing data;

a controller for controlling access to the flash memory and to the DRAM buffer in response to host reads and host writes received by the host interface, the controller writing host data to the DRAM buffer;

an SEED Solid-State Drive (SSD) Endurance Translation Layer (ETL) implemented in the DRAM buffer and controlled by the controller that uses the ETL to provide temporary storage to reduce flash wear;

a data write cache stored in the DRAM buffer and managed by the controller;

a flash interface for erasing blocks and writing pages in the flash memory, wherein a block is a multiple of pages in size;

a flash memory for storing grouped meta pages from the SSD DRAM buffer;

using a backup power supply to power the DRAM buffer and the flash memory and the controller when power is lost, the backup power supply having a sufficient capacity for the controller to copy desired data in the ETL to the flash memory.

14. The SEED of claim 13 further comprising:

a spare/swap area in the DRAM buffer;

a controller that uses the spare/swap area in the DRAM buffer to merge valid data in the flash memory with new data to generate combined data when over-writing a full page or a partial page of an existing block in the flash memory by writing new data to a spare block in the DRAM buffer related to the existing block in the flash memory, and when the spare block is needed by additional new data for a different block in the flash memory, writing a combination of the spare block with the new data and data from the existing block in the flash memory into a swap block in the flash memory and marking a page status for pages of the existing block in the flash memory as a garbage page.

15. The SEED of claim 13 further comprising:

a bad page manager for tracking bad pages of the flash memory,

the bad page manager for performing a routine comprising;

when an erased block in the flash memory has been erased, increasing an erase count in an erase count table for the erased block;

reading a page status table for the erased block, the page status table having a plurality of page entries, each page entry storing a status for a page in the erased block, the status including an indication of a bad page or of a good page;

for each page in the erased block, reading the page entry for the page from the page status table;

when the page status from the page status table is bad, processing a next page;

when the page status from the page status table is good, counting a number of un-erased bits in the page;

when the number of un-erased bits exceeds a first threshold, changing the page status to indicate a bad page in the page entry and increasing a bad page count;

when the number of un-erased bits is between a first threshold and a second threshold, and the page status from the page status table indicates that error-correction code (ECC) protection is needed, processing a next page;

when the number of un-erased bits is between a first threshold and a second threshold, and the page status from the page status table indicates that ECC protection is not needed, changing the page status in the page entry to indicate that ECC protection is needed by marking its page status as protect page and increasing an ECC protection page count;

when the bad page count for the erased block exceeds a third threshold, indicating that the erased block is a bad block and not writing new data to the erased block by marking its page status as bad page,

whereby bad erased blocks are identified by counting bad pages within the erased block and allowing bad pages to exist in a good block to prolong flash endurance.

16. The SEED of claim 15 further comprising:

an ECC generator that generates an ECC code having more bits per unit of data stored in the flash memory for pages having a lower reliability; and

a LDPC generator, activated by an ECC manager, for generating a Low-Density parity Check (LDPC) code for data having a high reliability in the flash memory;

whereby ECC code is dynamic.

17. A Virtual-Memory Device (VMD) driver for executing on a host comprising:

a host Endurance Translation Layer (ETL) executing on the host, the host ETL for increasing endurance of a flash memory having a low specified erase-cycle lifetime;

a host dynamic-random-access memory (DRAM) buffer on the host, the host DRAM buffer controlled by a host controller that uses the host ETL to provide temporary storage on the host to reduce flash wear;

a Super Enhanced Endurance Device (SEED) on a Solid-State Drive (SSD) on a SSD, the SEED for increasing endurance of the flash memory that has the low specified erase-cycle lifetime; and

a SEED Endurance Translation Layer (ETL) in a SEED DRAM buffer that is controlled by a SEED controller, the SEED ETL providing temporary storage to reduce flash wear.

18. The VMD driver of claim 17 further comprising:

a flush manager for flushing data stored in the host ETL of the host DRAM buffer to the SEED ETL in the SEED DRAM buffer and then to the flash memory of a flash drive system when power is lost;

a resume manager reloader for fetching flushed data from flash memory of the flash drive system and in the SEED ETL in the SEED DRAM buffer and then to the host ETL in the host DRAM buffer when power is restored.

19. The VMD driver of claim 17 further comprising:

a system transaction manager for creating logs to track a persistency of write activities to the SSD and for periodically setting up checkpoints to remove completely finished transactions; and

a SSD transaction manager for creating logs to tracks a persistency of write activities to the flash memory and for periodically setting up checkpoints to remove completely finished transactions.

20. The VMD driver of claim 17 further comprising a house cleaning procedure on the host which comprises:

obtaining a last access date of a file;

using a current date to calculate a delay time since the last access date of the file;

when the delay time exceeds a time threshold, deleting the file when an auto-clean setting is enabled and the file has a file type of temporary, log, or paging;

searching for duplicates of the file and deleting the duplicates;

repeating for other files on the host.

21. A Virtual-Memory Device (VMD) driver for executing on a host comprising:

an encryption engine, coupled to receive intercepted high-level host writes, for generating encrypted data;

a compression engine, coupled to receive intercepted high-level host writes, for generating compressed data;

a data write cache for storing host write data;

a data read cache for storing data for reading by the host;

a grouping engine for grouping data stored in the data write cache into meta-pages;

an un-grouping engine for un-grouping data in stored in meta-pages into ungrouped data for storage in the data read cache;

wherein meta-pages are sent from the grouping engine to a volume manager for transfer to a flash memory, and meta-pages stored in the flash memory are received by the un-grouping engine;

a power monitor for detecting a power failure;

a host dynamic-random-access memory (DRAM) buffer for storing a host Endurance Translation Layer (ETL);

a flush manager for flushing data stored in the host ETL of the host DRAM buffer to a Solid-State Drive (SSD) ETL DRAM and then to a flash memory of a Solid-State Drive (SSD) system when power is lost;

a resume manager reloader for fetching flushed data from the flash memory of the SSD system and then to the host ETL of the host DRAM buffer when power is restored.

22. The VMD driver of claim 21 further comprising:

a transaction manager for logging events indicating start and completion of data writes to the flash memory; and

a recovery manager for reading events logged by the transaction manager to undo or redo writes to the flash memory after power resumes.

23. An endurance flash file system comprising:

an upper-level file filter driver, for executing on a host, for intercepting high-level host writes to a flash drive;

an encryption/decryption engine, coupled to receive high-level host writes intercepted by the upper-level file filter driver, for generating encrypted data and for decrypting encrypted data;

a compression/decompression engine, coupled to receive high-level host writes from the upper-level file filter driver, for generating compressed data and for decompressing compressed data;

wherein compressed data and encrypted data are sent to a File System Driver (FSD) executing on the host;

a lower-level file filter driver, for executing on the host, for intercepting lower-level file system host writes to a flash drive system;

a data write cache for storing host write data;

a data read cache for storing data for reading by the host;

a grouping engine for grouping data stored in the data write cache into meta-pages;

an un-grouping engine for un-grouping data in stored in meta-pages into ungrouped data for storage in the data read cache;

wherein meta-pages are sent from the grouping engine to a volume manager for transfer to a flash memory, and meta-pages stored in the flash memory are received by the un-grouping engine;

a file priority tag sorter for generating a data type for a host write received;

a task policy assignor for assigning a priority to tasks including writing of host write data by the data type, wherein priority is a function of the data type from the file priority tag sorter;

a performance adjustor for adjusting priority of tasks;

a target assignor for sorting host write data based on the data type generated by the file priority tag sorter;

a transaction system for logging events indicating start and completion of data writes to the flash memory;

a flush manager for flushing data stored in a host DRAM to a SSD DRAM and then to a flash memory of a flash drive system when power is lost;

a resume manager reloader for fetching flushed data from the flash memory of the flash drive system and then to the host DRAM when power is restored; and

a disk miniport driver for managing vendor-specific functions of the flash drive system.

24. A Super Enhanced Endurance Device (SEED) comprising:

a host interface for receiving host reads and host writes from a host;

a dynamic-random-access memory (DRAM) buffer for storing data;

a controller for controlling access to the flash memory and to the DRAM buffer in response to host reads and host writes received by the host interface, the controller writing host data to the DRAM buffer;

an enhanced flash portion of a flash memory configured for use as a strong page;

a program/erase manager for controlling a page write/block erase time of the flash memory to increase endurance and decrease retention;

a refresh manager for controlling a refresh time for retention in the enhanced flash.