User Manual

Constellation.2 SAS Product Manual, Rev. K 23
Error rate is the number of errors per operation. The algorithm that S.M.A.R.T. uses to record rates of error is to set
thresholds for the number of errors and their interval. If the number of errors exceeds the threshold before the interval
expires, the error rate is considered to be unacceptable. If the number of errors does not exceed the threshold before
the interval expires, the error rate is considered to be acceptable. In either case, the interval and failure counters are
reset and the process starts over.
Predictive failures
S.M.A.R.T. signals predictive failures when the drive is performing unacceptably for a period of time. The firmware
keeps a running count of the number of times the error rate for each attribute is unacceptable. To accomplish this, a
counter is incremented each time the error rate is unacceptable and decremented (not to exceed zero) whenever the
error rate is acceptable. If the counter continually increments such that it reaches the predictive threshold, a predictive
failure is signaled. This counter is referred to as the Failure History Counter. There is a separate Failure History Counter
for each attribute.
5.2.5 Thermal monitor
Constellation®.2 drives implement a temperature warning system which:
1. Signals the host if the temperature exceeds a value which would threaten the drive.
2. Signals the host if the temperature exceeds a user-specified value.
3. Saves a S.M.A.R.T. data frame on the drive which exceeds the threatening temperature value.
A temperature sensor monitors the drive temperature and issues a warning over the interface when the temperature
exceeds a set threshold. The temperature is measured at power-up and then at ten-minute intervals after power-up.
The thermal monitor system generates a warning code of 01-0B01 when the temperature exceeds the specified limit
in compliance with the SCSI standard. The drive temperature is reported in the FRU code field of mode sense data. You
can use this information to determine if the warning is due to the temperature exceeding the drive threatening tem-
perature or the user-specified temperature.
This feature is controlled by the Enable Warning (EWasc) bit, and the reporting mechanism is controlled by the
Method of Reporting Informational Exceptions field (MRIE) on the Informational Exceptions Control (IEC) mode page
(1Ch).
The current algorithm implements two temperature trip points. The first trip point is set at 68°C. The second trip point
is user-selectable using the Log Select command. The reference temperature parameter in the temperature log page
(see Table 1) can be used to set this trip point. The default value for this drive is 68°C, however, you can set it to any
value in the range of 0 to 68°C. If you specify a temperature greater than 68°C in this field, the temperature is rounded
down to 68°C. A sense code is sent to the host to indicate the rounding of the parameter field.
Table 1: Temperature Log Page (0Dh)
Parameter Code Description
0000h
Primary Temperature
0001h
Reference Temperature