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 8,954,654 B2
• Filed: 12/28/2012
• Issued: 02/10/2015
• 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
• Primary Examiner(s): TSAI, SHENG JEN
• Application Number:
  US13/730,797
• Publication Number:
  US 20130145085A1
• Time in Patent Office: 774 Days
• Field of Search: 711/103
• 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.