Error Rates - Western Digital Re EX800M Technical Reference Manual

Reliability
4.2.1
Error Rates are specified as based upon ECC On-The-Fly data correction, automatic retries being
allowed, and all drive flaws reallocated.
Recoverable Read error rate:
Unrecoverable Read error rate:
Mis-corrected Read error rate:
Interface Error Rate:
4.2.1.1
A seek error is defined as a failure to position a head over the addressed track. As stated by the seek error
rate above, if the drive detects a seek error it will automatically perform an error recovery procedure. If
this error recovery fails, this is deemed an unrecoverable seek error and the drive will report back an
'04'h sense key; these errors are classified as a drive failure as defined within our MTBF specification.
4.2.1.2
A typical read can return data at a rate as defined in our performance section without additional drive
delay. This capability is based upon the LDPC (Low Density Parity Check) Channel technology
which provides data with ECC On-The-Fly data correction capability.
Beyond this on-the-fly capability, read errors can occur and are defined as follows:
Recoverable – whereby the drives error recovery procedure is required to correctly return the data after
an initial error condition was encountered.
Unrecoverable – whereby the drives error recovery procedures are unable to correctly return the data
requested; this data should be allocated to a new area of the drive.
Mis-corrected – as specified in the error rate above the frequency for this type of occurrence is
extremely rare. This type of event can occur as it relates to the tradeoffs of the channel technology
engine against the quantity, lengths, and patterns of data errors which may occur within a sector. As
mentioned above the LDPC channel is required to enable the recoverable and unrecoverable error rates
as specified above.
Before measuring read error rates, ensure that:
1. The data that is being used for measurement of read error rates must be verified that it is written
correctly on the media.
2. All media defect induced errors must be excluded from error rate calculations.
4.2.1.3
An interface error is defined as when the drive receiver detects errors of the incoming data whereby the
drive in unable to recover the data as transmitted to the receiver. These errors can include any of:
running disparity errors, illegal code, loss of word sync, or CRC errors.
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Error Rates

Seek Errors
Read Errors
Interface Errors
RELEASED 8/13/13
Less than 1 error in 10 12 bits transferred
Less than 10 in 10 16 bits transferred
Less than 1 sector in 10 26 bits transferred
Less than 1 error in 10 12 bits transferred
EX800M
2679-771339-A05