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2.6 Reliability
Table 2-12: Reliability Specifications
Nonrecoverable read errors (UBER)
1
<1 sector in 10
17
bits read, max
Mean Time Between Failures (MTBF)
2
Write or Erase Endurance
4
(specified by the flash component)
~ 2% between least worn and most worn cell
Data retention See Note 5
Notes:
1. Uncorrectable Bit Error rate (UBER) will not exceed one sector in the specified number of bits read. In the
extremely unlikely event of a non-recoverable read error, the drive will report it as a read failure to the host;
the sector in error is considered corrupt and is not returned to the host.
2. MTBF is calculated based on a Part Stress Analysis. It assumes nominal voltage, with all other parameters
within specified range. Telcordia method SR-332, component FIT rate at 55
o
c.
3. Power On/Off Cycles defined as power being removed from the drive, and then restored. Note that host
systems and drive enclosures may remove power from the drive for reasons other than a system
shutdown.
4. SLC NAND has a higher write/erase cell endurance than MLC NAND; varies by NAND component.
5. 10 years for P-E cycle counts < 10% of NAND spec and 1 year for max-spec P-E cycle counts per JEDEC-
STD-JESD47) Refer to Viking Application Note AN0011 – Flash Data Retention
2.6.1 Data, MetaData, and Firmware Code Protection
Element SSD implements data protection throughout its data path. Protection
techniques include:
• Data ECC Algorithms
• Datapath CRC Error Detection
• RAISE
TM
Data Protection Against Catastrophic Flash Page/Block Failure
2.6.1.1 DATA ECC Algorithms
The following data error correction is provided:
• For Flash memory devices providing 128 bytes of redundancy per 4k of
data (normally this is SLC Flash)
o 16 bytes of redundancy applied to 512 bytes of data
o Up to seven 9-bit symbols (up to 63 bits if contiguous) correctable
• For Flash memory devices providing 218 or more bytes of redundancy per
4k of data (normally this is MLC Flash)
o 27 bytes of redundancy applied to 512 bytes of data
o Up to twelve 9-bit symbols (up to 108 bits if contiguous) correctable
