FlashBus™ is a patented BiTMICRO® technology used internally in all E-Disk® and E-Disk® Altima™ product lines. A custom, intermediate Flash-bus between device-specific buffers and Flash-intelligent DMA controllers is employed to carry commands, addresses and data between the DMA controller and buffer chips.
Four-way interleaving of data between the buffer chips and Flash memory banks, coupled with time-multiplexed busy signaling for the whole bus, delivers unprecedented media transfer rates in the solid state drive industry.
Patented PowerGuard®
PowerGuard® is a patented intelligent internal power source that is added on to a standard E-Disk® and E-Disk® Altima™ solid state drive as an extra layer of optional hardware and firmware utilities. It is used:
to ensure that all data in the BiTMICRO solid state drive cache are stored into Flash memory without being lost or corrupted in the event of ungraceful power shutdowns; and/or
to securely erase all data in the BiTMICRO solid state drive quickly and irretrievably, if the user chooses to do so. Erasure of data can be done manually or automatically, locally via a command through the system interface or even independently of the host system or presence of an external power source.
PowerGuard® Levels and Operating Modes
PowerGuard® offers three different levels of data protection, namely: PowerGuard® I, PowerGuard® II and PowerGuard® III.
PowerGuard® III offers the highest level of data protection. It incorporates a 3-position manual switch that is located on the mechanical assembly containing the charge-carrying devices and its associated circuitry. This allows the user to select any of the three operating modes:
Save Mode
All data in the write dirty cache is automatically transferred from volatile to non-volatile memory in the event of external power degradation or loss.
Erase Mode
All data is completely and irretrievably erased from the non-volatile memory in the event of external power degradation or loss.
Standby Mode
PowerGuard®initiates system shut down upon external power degradation or loss. Standby mode allows the disk to be removed from the external power source and transported for an extended amount of time, while maintaining the ability to erase all the non-volatile memory upon activation of an easily accessible push button switch.
PowerGuard® II supports either Save or Erase Mode while PowerGuard® I comes only with Save Mode.
Patented securErase®
Certain applications managing highly sensitive data require the ability to erase all data from a drive, rapidly and without possibility of retrieval as a last resort. Typical 'disk shredding' utilities attempt to overwrite the data to render it beyond recoverability.
Unfortunately, technology is available today to recover data from hard disk drives and even DRAM-based (volatile) SSDs even after shredding because of traces left from the effects of hysteresis. Erasing drive data beyond recovery requires that each storage element be cycled repeatedly five or six times, which takes a considerable amount of time. As a result, BiTMICRO® developed and patented securErase®, a firmware utility that erases all traces of data (except wear leveling statistical data) on each block of non-volatile memory efficiently and effectively. securErase® is fully compliant with the remanence security requirements of the U.S. DoD, NSA, Air Force, Army and Navy.
When used in combination with PowerGuard® II Erase mode, securErase® is executed as soon as the system powers down and automatically resumes the erase procedure upon power up. On an E-Disk® and E-Disk® Altima™ solid state drive with PowerGuard® III in Standby mode, securErase® may be executed by either depressing the external push button or by toggling the 3-way mode select switch from Standby Mode to Erase Mode. If for any reason the erase process fails to complete, securErase® automatically resumes the erase procedure upon power up.
The standard erase facility (via a SCSI/IDE erase command) is provided in all BiTMICRO® Flash solid state drives.
DataSentinel
Any storage peripheral that does not employ any method of buffering between the storage medium and the system interface will suffer in terms of poor I/O performance. E-Disk® and E-Disk® Altima™ solid state drives employ a small amount of DRAM to serve as high-speed cache for implementing its write policies.
Given the volatile nature of DRAM, BiTMICRO developed DataSentinel to maintain standards of high performance without necessarily compromising data integrity. To reduce risk of data loss during low voltage and brownout situations, DataSentinel provides the following standard and user-programmable functions:
Low Voltage Detection
Input voltage sensors enable the E-Disk® and E-Disk Altima™ solid state drive to prevent data corruption or data loss due to unexpected power interruptions. As a precautionary measure, flushing of cache contents is initiated, and succeeding writes are directed to non-volatile storage immediately upon detection of non-critical low input voltage. Detection of critical low input voltage level halts all data-related operations until input voltage stabilizes. These reduce the risk of data corruption to file allocation (FAT) or translation tables in the event of an aborted write operation. Peripherals that do not have any low voltage detection logic are more exposed to data corruption because device writes are allowed to continue during low voltage conditions.
Redundant Pre-Write
The E-Disk® and E-Disk® Altima™ solid state drive allocates a number of reserved memory blocks for use as a scratchpad and for internal translation tables. This BiTMICRO® Networks proprietary feature pre-writes modifications to the translation tables to the scratchpad area.
Concurrent-Multiple Write
This feature reduces the risk of data and FAT corruption due to low voltage writes by reducing the "window of vulnerability" or window of time that the Flash device spends in the write phase.
Cache-on-Write Disable When the user disables Cache-on-Write mode, data integrity is guaranteed because it is written directly to Flash memory before sending a positive acknowledgment to the host. There is however a severe penalty in write performance when selecting this mode. Read performance is not affected since read cycles still see the full cache size.
DataSentinel is a value-added feature in all E-Disk® Altima™ solid state drives.
Patented Wear Leveling
BiTMICRO's device firmware has special algorithms to distribute erase/write cycles evenly across all Flash memory block locations. As per Flash memory specifications, it can be determined that the write cycle endurance of a 64GB E-Disk is 2630 years at 100GB per day erase/write cycles. The endurance of E-Disk® and E-Disk® Altima™ solid state drives can be extended by at least a factor of 15 times when used in conjunction with intelligent maintenance features such as BCH ECC threshold tuning, flash memory scrubbing and fully associative caching.
To ensure the reliability of data stored in the E-Disk® Altima™ flash solid state drive, BiTMICRO engineers have adopted the Bose-Chaudhuri-Hocquenghem (BCH) Error Correction Code. BCH-ECC is a family of powerful cyclic block forward error correction codes used in the transmission of data.
By implementing the built in BCH EDC/ECC algorithm in every E-Disk® Altima™ solid state drive, up to 10 bit errors can be detected and up to 9 random bit errors are corrected per 528-byte block.
Sectioning and Flash Pre Erase
These features address performance and endurance issues and challenges caused by the growing sizes of flash “erase blocks” by providing sectioning to emulate the small blocks. Data can simply be modified without the need to erase the whole block prior to a write operation, thus improving disk utilization and further extending the wear-out life of the drive
Moreover, the E-Disk® Altima™ solid state drive allocates pre-erased flash blocks where data can be written faster, eliminating the need to perform an erase operation immediately before a write operation.
Flash Memory Scrubbing
A feature of all BiTMICRO® E-Disk® and E-Disk® Altima™ solid state drives is the firmware that automatically monitors and corrects errors in every location of Flash memory. Patented Flash Memory Scrubbing, performed in the background during host I/O inactivity, globally cleans up all flash memory blocks, correcting single bit errors, and preventing these single bit errors from accumulating into uncorrectable multiple bit errors.
Wear-Out Monitor
A feature of all E-Disk® and E-Disk® Altima™ solid state drive is the proprietary BiTMICRO firmware that monitors how much block erase/write wear-out has been accumulated by the drive. The drive provides a special LED signal warning when the total number of writes has reached 95% of the recommended operating threshold. Note that the E-Disk® Altima™ solid state drives' erase/write cycles can exceed this threshold.
Automatic Bad Block Remapping
Due to normal wear and tear, there will always be a possibility that the E-Disk® and E-Disk® Altima™ solid state drive encounters bad memory blocks as Flash memory approaches its write/erase cycle endurance limit. Remapping is performed by firmware on the fly to replace logical block address entries that point to bad blocks with new good blocks. BiTMICRO's solid state drives are shipped with a number of good reserved blocks for this purpose.
Save Mode