Flash-Memory Device with RAID-type Controller

• US 20120278543A1
• Filed: 06/12/2012
• Published: 11/01/2012
• Est. Priority Date: 02/22/2007
• Status: Active Grant

• Current Assignee: Super Talent Technology, Corporation
• Original Assignee: Super Talent Electronics, Inc.
• Inventors: Yu, Frank, Ma, Abraham C., Chen, Shimon
• Granted Patent: US 8,543,742 B2
• Time in Patent Office: Days
• US Class Current: 711/103
• CPC Class Codes: G06F 11/1064 in cache or content addressable memories
• CPC Class Codes: G06F 12/0246 in block erasable memory, e.g. flash memory
• CPC Class Codes: G06F 12/0607 Interleaved addressing
• CPC Class Codes: G06F 13/28 using burst mode transfer, e.g. direct memory access DMA, cycle steal G06F13/32 takes precedence
• CPC Class Codes: G06F 13/385 for adaptation of a particular data processing system to different peripheral devices
• CPC Class Codes: G06F 2212/7208 Multiple device management, e.g. distributing data over multiple flash devices
• CPC Class Codes: G06F 2212/7211 Wear leveling
• CPC Class Codes: G06F 2213/3802 Harddisk connected to a computer port
• CPC Class Codes: G06F 3/0604 Improving or facilitating administration, e.g. storage management
• CPC Class Codes: G06F 3/0658 Controller construction arrangements
• CPC Class Codes: G06F 3/0688 Non-volatile semiconductor memory arrays

Abstract

A smart flash drive has one or more levels of smart storage switches and a lower level of single-chip flash devices (SCFD'"'"'s). A SCFD contains flash memory and controllers that perform low-level bad-block mapping and wear-leveling and logical-to-physical block mapping. The SCFD report their capacity, arrangement, and maximum wear-level count (WLC) and bad block number (BBN) to the upstream smart storage switch, which stores this information in a structure register. The smart storage switch selects the SCFD with the maximum BBN as the target and the SCFD with the lowest maximum WLC as the source of a swap for wear leveling when a WLC exceeds a threshold that rises over time. A top-level smart storage switch receives consolidated capacity, arrangement, WLC, and BBN information from lower-level smart storage switch. Data is striped and optionally scrambled by Redundant Array of Individual Disks (RAID) controllers in all levels of smart storage switches.

Claims

1. A smart flash drive comprising:

a top-level smart storage switch that is connected upstream to a host and has a plurality of downstream interfaces;

a plurality of second-level smart storage switches each having an upstream interface to the top-level smart storage switch and a plurality of downstream interfaces;

an operation unit, in a data path of the top-level smart storage switch, for performing an operation upon data to be stored in a physical block of flash memory, wherein the operation is a compression or an encryption;

a plurality of single-chip flash devices (SCFD'"'"'s), a SCFD comprising;

a plurality of physical blocks of flash memory;

a low-level wear-level controller that performs wear-leveling swapping of physical blocks within that SCFD based on a wear-level count (WLC) for each physical block;

a low-level mapper that maps a low-level logical address to a physical-block address (PBA) for physical blocks within the SCFD;

a top-level Redundant Array of Individual Disks (RAID) controller, in the top-level smart storage switch, the top-level RAID controller striping host data into a plurality of top-level stripes to the plurality of second-level smart storage switches

a plurality of second-level RAID controllers in the plurality of second-level smart storage switches, wherein a second-level RAID controller stripes data received on the upstream interface of a second-level smart storage switch into a plurality of second-level stripes to the plurality of SCFD connected to the second-level smart storage switch; and

an interleaving controller, in the SCFD, for interleaving data received by the SCFD across multiple planes of flash memory.

2. The smart flash drive of claim 1 wherein the top-level smart storage switch reserves a first reserved area of the plurality of physical blocks of flash memory in the a plurality of SCFD'"'"'s, the first reserved area for storing overhead management information used by the top-level smart storage switch, the first reserved area not reported to the host as available memory;

wherein a second-level smart storage switch reserves a second reserved area of the plurality of physical blocks of flash memory in the a plurality of SCFD'"'"'s, the second reserved area for storing overhead management information used by the second-level smart storage switch, the second reserved area not reported to the top-level smart storage switch as available memory;

wherein the SCFD reserves a third reserved area of the plurality of physical blocks of flash memory in the a plurality of SCFD'"'"'s, the third reserved area for storing overhead management information used by the SCFD, the third reserved area not reported to the second-level smart storage switch as available memory,

whereby three levels of reserved areas are stored in the SCFD for use by three levels of controllers.

3. The smart flash drive of claim 2 wherein a channel size is a size of a physical block of flash memory multiplied by a number of planes interleaved by the interleaving controller;

wherein a top-level stripe size is a number of SCFD connected to the second-level smart storage switch.

4. The smart flash drive of claim 3 wherein the SCFD further comprises:

a low-level wear-level controller that performs wear-leveling swapping of physical blocks within that SCFD based on a wear-level count (WLC) for the physical block;

a bad-block manager that disables and counts bad blocks within the SCFD to generate a bad-block number (BBN) for the SCFD.

5. The smart flash drive of claim 4 wherein the SCFD reports a maximum WLC and a BBN to an upstream second-level smart storage switch;

wherein the second-level smart storage switch further comprises;

a structure register that stores the maximum WLC and the BBN for all SCFD connected to the second-level smart storage switch.

6. The smart flash drive of claim 5 wherein the top-level smart storage switch further comprises:

a top-level structure register that stores the maximum WLC and a maximum BBN reported by the second-level smart storage switch connected to the top-level smart storage switch.

7. The smart flash drive of claim 6 wherein the second-level smart storage switch further comprises:

a mid-level wear leveler, reading the maximum WLC and BBN from the structure register, and comparing the maximum WLC to a WLC threshold to activate a wear-leveling swap when one of the maximum WLC stored in the structure register exceeds the WLC threshold; and

a direct-memory access (DMA) engine that is programmed to swap data from a source physical block in a target SCFD that has a BBN that is a largest BBN stored in the structure register, the DMA engine swapping data to a target physical block in a source SCFD that has a maximum WLC that is lower than other maximum WLC stored in the structure register;

whereby physical blocks of flash memory in the SCFD are wear-leveled by the second-level smart storage switch that examines maximum WLC and BBN stored in the structure register.

8. A smart flash device comprising:

a plurality of single-chip flash devices (SCFD'"'"'s), a SCFD comprising;

a plurality of physical blocks of flash memory;

a low-level wear-level controller that performs wear-leveling swapping of physical blocks within that SCFD based on a wear-level count (WLC) for the physical block;

a low-level mapper that maps a low-level logical address to a physical-block address (PBA) for physical blocks within the SCFD;

a bad-block manager that disables and counts bad blocks within the SCFD to generate a bad-block number (BBN) for the SCFD;

wherein the SCFD generates a maximum WLC from the WLC for physical blocks in the SCFD and reports over an upstream interface the maximum WLC and the BBN;

a low-level smart storage switch that comprises;

a plurality of SCFD drivers, a SCFD driver for connecting to a SCFD in the plurality of SCFD;

an upstream interface that receives data from an upstream device;

a controller that stripes the data from the upstream device among the plurality of SCFD, wherein a stripe size is equal to a channel size of the SCFD;

a structure register that stores the maximum WLC and the BBN for the plurality of SCFD connected to the low-level smart storage switch;

a mid-level wear leveler, reading the maximum WLC and BBN from the structure register, having a comparator that compares the maximum WLC to a WLC threshold and activates a wear-leveling swap when one of the maximum WLC stored in the structure register exceeds the WLC threshold; and

a direct-memory access (DMA) engine that is programmed to swap data from a source physical block in a target SCFD that has a BBN that is a largest BBN stored in the structure register, the DMA engine swapping data to a target physical block in a source SCFD that has a maximum WLC that is lower than other maximum WLC stored in the structure register,

whereby physical blocks of flash memory in the SCFD are wear-leveled by the low-level smart storage switch that examines maximum WLC and BBN stored in the structure register.

9. The smart flash device of claim 8 further comprising:

a plurality of the low-level smart storage switches that connect to a top-level smart storage switch;

wherein a low-level smart storage switch generates a maximum WLC and a maximum BBN stored in its structure register and reports to the top-level smart storage switch the maximum WLC and the maximum BBN;

wherein the top-level smart storage switch comprises;

an upstream interface that receives data from a host;

a top-level controller that stripes the data from the host among the plurality of low-level smart storage switches, wherein a top-level stripe size is equal to the channel size of the SCFD multiplied by a number of SCFD connected to the low-level smart storage switch;

a top-level structure register that stores the maximum WLC and the maximum BBN for the low-level smart storage switches connected to the top-level smart storage switch;

a top-level wear leveler, reading the maximum WLC and the maximum BBN from the top-level structure register, having a comparator that compares the maximum WLC to a WLC threshold and activates a wear-leveling swap when one of the maximum WLC stored in the structure register exceeds the WLC threshold; and

a top-level direct-memory access (DMA) engine that is programmed to swap data from a source physical block in a target SCFD connected to a low-level smart storage switch that has the maximum BBN that is a largest BBN stored in the structure register, the DMA engine swapping data to a target physical block in a source SCFD connected to a low-level smart storage switch that has a maximum WLC that is lower than other maximum WLC stored in the structure register;

an operation unit, in a data path of the top-level smart storage switch, for performing an operation upon data to be stored in a block in the physical blocks of flash memory, wherein the operation is a compression or an encryption;

whereby wear-leveling is performed at a top-level, a mid-level, and within the SCFD.

10. The smart flash device of claim 9 wherein the WLC threshold is increased when the WLC threshold is reached;

wherein a BBN threshold is increased when the BBN threshold is reached.

11. The smart flash device of claim 9 wherein the controller further comprises a striping scrambler that scrambles assignment of data striped to the plurality of SCFD,

whereby data is scrambled and striped to the SCFD.

12. The smart flash device of claim 11 wherein the top-level smart storage switch scrambles assignment of data to the plurality of low-level smart storage switches;

wherein the low-level smart storage switches each scramble assignment of data to the plurality of SCFD attached to the low-level smart storage switch,

whereby data assignments are scrambled at two levels of smart storage switches.

13. The smart flash device of claim 11 wherein the controller further comprises a security key driver and a key storage, wherein a password or challenge number from the host is verified using a security algorithm executing on the controller.

14. The smart flash device of claim 13 wherein program execution on the host is disabled when the controller is unable to verify the password or challenge number.

15. A multi-level flash device comprising:

a top-level smart storage switch comprising a smart storage switch connected upstream to a host and downstream to a plurality of second-level smart storage switches;

wherein a second-level smart storage switch in the plurality of second-level smart storage switches comprises a smart storage switch connected downstream to a plurality of endpoint devices and upstream to the top-level smart storage switch;

wherein an endpoint device comprises a single-chip flash device (SCFD) having physical blocks of flash memory;

wherein the smart storage switch comprises;

downstream means for connecting to a plurality of downstream devices;

upstream means for connecting to an upstream device;

controller means for dividing upstream data into a plurality of stripes, each stripe being sent to a different downstream device;

structure register means for storing wear-level counts and bad-block counts received from downstream devices;

upstream reporting means for reporting a maximum of the wear-level counts to the upstream device and for reporting a maximum of the bad-block counts to the upstream device;

wear leveling means for swapping physical blocks of two downstream devices selected using the wear-level counts and bad-block counts stored in the structure register means,

encryptor/decryptor means, in a data path of the top-level smart storage switch, for encrypting data to be stored in a block in the physical blocks of flash memory, and for decrypting data read from a block in the physical blocks of flash memory,

whereby wear leveling is performed on multiple levels.

16. The multi-level flash device of claim 15 wherein the smart storage switch further comprises:

security means for executing a security function on an input number to generate an answer number, and for comparing the answer number to an expected answer to enable access to downstream SCFD or execution of a program on the host.

17. The multi-level flash device of claim 16 wherein the controller means further comprises:

scrambling means for scrambling assignment of stripes to downstream devices in a random sequence,

whereby data is scrambled on multiple levels during striping.

18. The multi-level flash device of claim 17 wherein the wear-leveling means further comprises:

register read means for reading the maximum WLC and a maximum BBN from the structure register means;

compared means for comparing the maximum WLC to a WLC threshold and for activating a wear-leveling swap when one of the maximum WLC stored in the structure register means exceeds the WLC threshold; and

direct-memory access (DMA) engine means, programmed to swap data from a source physical block in a target SCFD connected to a second-level smart storage switch that has the maximum BBN that is a largest BBN stored in the structure register means, for swapping data to a target physical block in a source SCFD connected to a second-level smart storage switch that has a maximum WLC that is lower than other maximum WLC stored in the structure register means.