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2.6.1.2 Data Path CRC Error Detection
CRC error detection is applied against data along internal data paths. CRC
detection uses a 32-bit checksum (CRC32) to protect data along all internal data
paths to correct silent errors not detected by other schemes.
2.6.1.3 RAISE
TM
Data Protection Against Catastrophic Flash Page/Block
Failure
Element SSD implements proprietary R.A.I.S.E.
TM
(Redundant Array of
Independent Silicon Elements) data protection, to overcome the probabilistic risk
of page or block failure inherent in all Flash memory technology.
Flash technology can exhibit a finite probability that a block or page will fail within
the rated Program-Erase (P-E) cycle count lifetime of the Flash device. While this
probability may appear tolerable for a given application, note that it is for a
particular Flash die. For an SSD incorporating up to 128 Flash die, the additive
probability of this phenomenon can reveal measurable risk to the SSD over its
multi-year lifetime.
Element SSD technology addresses this risk. In the event of a catastrophic
failure of an entire Flash page or Flash block, RAISE
TM
off-line protection rebuilds
the data in the failed page or block and relocates it elsewhere in the Flash array.
Performance during recovery is impacted, but after recovery is complete,
Element SSD returns to full performance and full functionality. The performance
impact period is only the amount of time required to rebuild and relocate the page
or block data, and to map out the problematic Flash block.
In contrast to other SSD Flash controllers, Element SSD with RAISE
TM
technology uniquely, reliably and seamlessly overcomes these catastrophic data
loss risks with only temporary impact to throughput and latency and no impact to
power consumption. In a RAID drive array application, Element SSD can auto-
rebuild data locally, without passing the problem upstream to the system level
and without incurring the associated significant system rebuild hit. The difference
in impact between a standard approach and Element SSD with RAISE
TM
approach is significant. Additionally, following recovery from a page failure or
block failure, Element SSD is fully functional and fully reliable, whereas a page-
failed or block-failed drive recovered by system RAID must be immediately
replaced.
2.6.1.4 Firmware Code Protection
Firmware requires special attention to ensure the code is execution-worthy. For
this reason, firmware is stored in multiple redundant images in the Flash array.
Image checksums are compared between all stored copies to ensure identical
