hesela.devRaw bit error rate
Raw bit error rate is the number of erroneous bits divided by the total bits read at a specified measurement point before error correction.
RBER includes errors that correction subsequently repairs. Report sensing conditions, the observation interval and the actual counters. The FAST 2016 first-generation devices recorded only the worst-chunk count among 16 chunks per page: the full error count lies between that count and 16 times it, so the multiplier is a bound, not a calibration. Across-drive percentiles do not reveal the within-codeword error distribution. [1] BER comparisons require the same measurement boundary. [2]
Relations
- related
- bit-error-rate, uncorrectable-bit-error-rate, error-correcting-code, codeword, ldpc, read-retry
Limitations
- RBER alone is not a universal predictor of uncorrectable errors; the FAST 2016 Google fleet study found it was not predictive in that population. [1]
Citations
- Schroeder, Lagisetty and Merchant. Flash Reliability in Production: The Expected and the Unexpected. USENIX FAST 2016, sections 4 and 5.2-5.3.
- SNIA Dictionary: bit error rate.
- Hesela: LDPC in NAND, the read cost of confidence.
- Hesela: BCH, LDPC and the RBER aggregation trap; synthetic counting example, not fleet measurements.