Flash-memory device with RAID-type controller
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.
1. A Smart Storage Switch flash device comprising:
a smart storage switch connected upstream to an upstream device and downstream to a plurality of endpoint flash memories;
a flash memory which comprises a plurality of multiple Input/Outputs (I/Os) and a plurality of chip enables;
wherein the smart storage switch comprises:
downstream means for connecting to a plurality of downstream flash memories;
upstream means for connecting to an upstream device;
controller means for dividing upstream data received from the upstream device into a plurality of stripes, each stripe being sent to a different downstream flash memory;
structure register means for storing wear-level counts and bad-block counts of downstream flash memories;
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; and
wear leveling means for using a direct-memory access (DMA) engine to swap physical blocks of two downstream flash memory blocks in two different ones of the downstream flash memories selected using the wear-level counts and bad-block counts stored in the structure register means.
2. The Smart Storage Switch flash device of claim 1 further comprising an upstream interface having a protocol selected from the group consisting of Serial AT-Attachment (SATA), a Peripheral Components Interconnect Express (PCIe) bus, Compact Flash (CF) bus, Universal-Serial-Bus (USB), Secure Digital (SD), e-Multi-Media Card (eMMC) bus, Serial-Attached Small-computer system interface (SAS), and Micro-SD.