User Manual

Constellation.2 SAS Product Manual, Rev. K 24
5.2.6 Drive Self Test (DST)
Drive Self Test (DST) is a technology designed to recognize drive fault conditions that qualify the drive as a failed unit.
DST validates the functionality of the drive at a system level.
There are two test coverage options implemented in DST:
1. Extended test
2. Short test
The most thorough option is the extended test that performs various tests on the drive and scans every logical block
address (LBA) of the drive. The short test is time-restricted and limited in length—it does not scan the entire media
surface, but does some fundamental tests and scans portions of the media.
If DST encounters an error during either of these tests, it reports a fault condition. If the drive fails the test, remove it
from service and return it to Seagate for service.
5.2.6.1 DST failure definition
The drive will present a “diagnostic failed” condition through the self-tests results value of the diagnostic log page if a
functional failure is encountered during DST. The channel and servo parameters are not modified to test the drive
more stringently, and the number of retries are not reduced. All retries and recovery processes are enabled during the
test. If data is recoverable, no failure condition will be reported regardless of the number of retries required to recover
the data.
The following conditions are considered DST failure conditions:
• Seek error after retries are exhausted
• Track-follow error after retries are exhausted
• Read error after retries are exhausted
• Write error after retries are exhausted
Recovered errors will not be reported as diagnostic failures.
5.2.6.2 Implementation
This section provides all of the information necessary to implement the DST function on this drive.
5.2.6.2.1 State of the drive prior to testing
The drive must be in a ready state before issuing the Send Diagnostic command. There are multiple reasons why a
drive may not be ready, some of which are valid conditions, and not errors. For example, a drive may be in process of
doing a format, or another DST. It is the responsibility of the host application to determine the “not ready” cause.
While not technically part of DST, a Not Ready condition also qualifies the drive to be returned to Seagate as a failed
drive.
A Drive Not Ready condition is reported by the drive under the following conditions:
• Motor will not spin
• Motor will not lock to speed
• Servo will not lock on track
• Drive cannot read configuration tables from the disk
In these conditions, the drive responds to a Test Unit Ready command with an 02/04/00 or 02/04/03 code.