Maxtor ATLAS 10K III Manual download pdf (Page 314)

Feature Descriptions

Quantum Atlas 10K II Ultra 160/m SCSI Hard Disk Drives 6-13

NOTE

In a multimode environment, any insertion or removal that changes the bus

mode causes a transceiver mode change reset event.

System Considerations

It is not possible for the suppliers of various system components (e.g., targets,

initiators, backplanes, terminators) to guarantee that a system can operate under

“Hot Swap Case 4” conditions. Therefore, the system integrator bears the

responsibility for ensuring that the system can meet “Hot Swap Case 4” operational

criteria.

There are two metrics key to ensuring “Hot Swap Case 4” tolerance:

1. When a drive is being hot inserted into an active bus, a smaller capacitance on

the SCSI bus pins create a smaller (that is, a lesser charge) transient spike on

the bus.

2. When the drive is the closest drive to the connector at which another drive is

being hot inserted, it is desirable that the input receivers ignore short low

amplitude transients (usually via a low pass filter).

LVD SCSI devices may require more stringent system design to tolerate transients

that occur during Case 4 insertion or removal. System integrators should consider

the following when designing their backplanes or buses:

1. Larger connector-to-connector spacing causes the transients associated with hot

swapping to be attenuated dramatically before reaching an operating drive.

2. Larger SCSI signal-trace capacitance (that is, lower impedance) is preferable for

minimizing transient spikes, but can cause other bus problems unrelated to hot

swapping. Draft standard SCSI-3 SCSI SPI-2 (SCSI Parallel Interface), Revision

18, Section 6.6.2 illustrates the tradeoffs between trace capacitance and drive-to-

drive spacing.

3. The universe of drives needs to be homogeneous. A 15 pF drive hot-inserted into

a rack of 15 pF drives presents no difficulty. A 30 pF drive inserted into a rack of

10 pF drives with very close connector spacing, however, is more likely to cause

problems.

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Maxtor ATLAS 10K III Manual Page 314