Seagate Cheetah ST3146854, User Manual

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Cheetah 15K.4 SCSI Product Manual, Rev. D 19
Case 4 - Current I/O process allowed during insertion or removal, except on the device being changed
Seagate Cheetah 15K.4 SCSI disc drives support all four hot plugging cases. Provision shall be made by the
system such that a device being inserted makes power and ground connections prior to the connection of any
device signal contact to the bus. A device being removed shall maintain power and ground connections after
the disconnection of any device signal contact from the bus (see SFF-8451 Specification for SCA-2 Unshielded
Connections).
It is the responsibility of the systems integrator to assure that no hazards from temperature, energy, voltage, or
ESD potential are presented during the hot connect/disconnect operation.
All I/O processes for the SCSI device being inserted or removed shall be quiescent. All SCSI devices on the
bus shall have receivers that conform to the SPI-4 standard.
If the device being hot plugged uses single-ended (SE) drivers and the bus is currently operating in low voltage
differential (LVD) mode, then all I/O processes for all devices on the bus must be completed, and the bus qui-
esced, before attempting to hot plug. Following the insertion of the newly installed device, the SCSI host
adapter must issue a Bus Reset, followed by a synchronous transfer negotiation. Failure to perform the SCSI
Bus Reset could result in erroneous bus operations.
The SCSI bus termination and termination power source shall be external to the device being inserted or
removed.
End users should not mix devices with high voltage differential (HVD) drivers and receivers and devices with
SE, LVD, or multimode drivers and receivers on the same SCSI bus since the common mode voltages in the
HVD environment may not be controlled to safe levels for SE and LVD devices (see ANSI SPI-4).
The disc drive spindle must come to a complete stop prior to completely removing the drive from the cabinet
chassis. Use of the Stop Spindle command or partial withdrawal of the drive, enough to be disconnected from
the power source, prior to removal are methods for insuring that this requirement is met. During drive insertion,
care should be taken to avoid exceeding the limits stated in Section 6.4.4, "Shock and vibration" in this manual.
5.2.4 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 drive degradation 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 instanta-
neous drive failures.
Each attribute monitors a specific set of conditions in the operating performance of the drive, and the thresh-
olds are optimized to minimize “false” 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 Rezero Unit command. Forc-
ing 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 Rezero Unit command will reset the timer.