HP SCSI Host Bus Adapters Table, NOTE:, Table, Table, Table, Example, (page 54), Table 5-2Domain Validation Fallback Levels, Example 5-2Typical Domain Validation syslog Entry

Table 5-1 Problems Detected By Domain Validation (continued)

Problem	Possible Cause
Excessive cross talk	Poor shielding or grounding.
Excessive system noise	Poor shielding or grounding.

When Domain Validation determines that communication with the target device is not possible at the maximum data transfer rate supported by the adapter (Ultra320), it writes a warning message to the /var/adm/syslog.log file. Example 5-2shows a typical log entry:

Example 5-2 Typical Domain Validation syslog Entry

SCSI Ultra320 0/3/1/1 instance 9:

Domain Validation forced SCSI Parameter fallback.

Target ID 2 - Currently operating at Ultra160 Wide.

The data transfer rate then “falls back” by one level to a slower setting. Table 5-2lists the fallback levels for most systems:

Table 5-2 Domain Validation Fallback Levels

SCSI Rate	Bus Width	Data Transfer Rate (MB/s)
Ultra320	Wide	320
Ultra160	Wide	160
Ultra2 Wide	Wide	80
Ultra2	Narrow	40
Ultra Wide	Wide	40
Ultra	Narrow	20
Fast Wide	Wide	20
Fast	Narrow	10
Asynchronous	Narrow	<5

NOTE: The number of entries in Table 5-2is subject to change. It is provided here to give you an example of how the fallback procedure works.

Domain Validation tests are run on all targets on the SCSI bus, even those targets that do not have Ultra320 capabilities. The starting point in Table 5-2depends on the parameters that were negotiated for any particular target. Since a SCSI bus can contain up to 15 targets, several different SCSI parameters may be in effect at any one time on the bus, because Domain Validation is running on all of the targets at the same time.

For example, if the parameters originally negotiated during the normal SCSI initiator/target communications are equivalent to Ultra320, but Domain Validation determines that the SCSI bus or the target cannot support that data transfer rate, then Domain Validation falls back to Ultra160. After the fallback, Domain Validation repeats its test. If the bus or target still cannot support the transfer rate, Domain Validation falls back another level, to Ultra2 Wide; then to Ultra2 Narrow, and so forth. As long as failures occur, fallback continues, one level at a time, until the lowest level in Table 5-2(Asynchronous) is reached. Note that Domain Validation does not generate a fallback warning message such as Example 5-2 (page 54) each time that it falls back a level, but only when it successfully settles at a level. If a failure occurs at the lowest level, the device is taken offline and a Domain Validation failure message is written to the /var/adm/syslog.log file. For example:

54 Troubleshooting