S.m.a.r.t - Seagate ST34501N Product Manual

Cheetah 4LP Product Manual, Rev. B
4. The SCSI device being removed or inserted shall employ transceivers that conform to the requirements for
glitch-free power-on/off in the SCSI-3 standard. The SCSI device shall maintain the high-impedance state
at the device connector contacts during a power cycle until the transceiver is enabled.
5. The power to the electronics and mechanics of the device may be simultaneously switched with the bus
contacts if the power distribution system is able to maintain adequate power stability to other devices dur-
ing the transition and the grounding requirements in items 2 and 3 are met.
6. The SCSI bus termination shall be external to the device being inserted or removed.
7. Connector J2 must be configured so there is no connection between the drive and TRMPWR signal on
SCSI bus. Removing all jumpers will accomplish this.
8. The disc drive motor must come to a complete stop prior to changing the plane of operation. This time is
required to insure data integrity.
Note. Hot-plug drives are not designed for simultaneous power disconnection and physical removal.
5.2.7

S.M.A.R.T.

S.M.A.R.T. is an acronym for Self-Monitoring Analysis and Reporting Technology. This technology is intended
to recognize conditions that indicate a drive failure and is designed to provide sufficient warning of a failure to
allow data back-up before an actual failure occurs.
Note. The firmware will monitor specific attributes for degradation over time but cannot predict instantaneous
drive failures.
Each attribute has been selected to monitor a specific set of failure conditions in the operating performance of
the drive, and the thresholds are optimized to minimize "false" and "failed" predictions.
Controlling S.M.A.R.T.
The operating mode of S.M.A.R.T. is controlled by the DEXCPT bit and the PERF bit of the "Informational
Exceptions Control Mode Page" (1Ch). The DEXCPT bit is used to enable or disable the S.M.A.R.T. process.
Setting the DEXCPT bit will disable all S.M.A.R.T. functions. When enabled, S.M.A.R.T. will collect on-line data
as the drive performs normal read/write operations. When the PERF bit is set, the drive is considered to be in
"On-line Mode Only" and will not perform off-line functions.
The process of measuring off-line attributes and saving data can be forced by the RTZ command. Forcing
S.M.A.R.T. will reset the timer so that the next scheduled interrupt will be two hours.
The drive can be interrogated by the host to determine the time remaining before the next scheduled measure-
ment and data logging process will occur. This is accomplished by a log sense command to log page 0x3E.
The purpose is to allow the customer to control when S.M.A.R.T. interruptions occur. As described above, forc-
ing S.M.A.R.T by the RTZ command will reset the timer.
Performance impact
S.M.A.R.T. attribute data will be saved to the disc for the purpose of recreating the events that caused a predic-
tive failure. The drive will measure and save parameters once every two hours subject to an idle period on the
SCSI bus. The process of measuring off-line attribute data and saving data to the disc is uninterruptable and
the maximum delay is summarized below:
Maximum processing delay
On-line only delay
DEXCPT = 0, PERF = 1
S.M.A.R.T. delay times 50 milliseconds
Reporting control
Reporting is controlled in the "Informational Exceptions Control Page" (1Ch). Subject to the reporting method,
the firmware will issue to the "host" an 01-5D00 sense code. The error code is preserved through bus resets
and power cycles.
Fully enabled delay
DEXCPT = 0, PERF = 0
200 milliseconds
15