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2.5.1.1 DATA ECC Algorithms
The following data error correction is provided:
• Up to 55 bytes of redundancy applied to 512 bytes of data
2.5.1.2 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.
2.5.1.3 RAISE
TM
Data Protection Against Catastrophic Flash Page/Block
Failure
R.A.I.S.E.
TM
(Redundant Array of Independent Silicon Elements) provides data
protection to overcome the probabilistic risk of page or block failure inherent in all
Flash memory technology. In a tiered approach to detecting and correcting
NAND errors, RAISE
TM
takes over where ECC leaves off.
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.
RAISE
TM
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 minimally impacted, but after recovery is
complete, Slim SATA 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, Slim SATA 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, Slim SATA 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 Slim SATA with RAISE
TM
approach is
significant. Additionally, following recovery from a page failure or block failure,
Slim SATA is fully functional and fully reliable, whereas a page-failed or block-
failed drive recovered by system RAID must be immediately replaced.
