LX0-103 · Question #142
You ran out of space and added a eighth disk to your SCSI-1 system. When you try to start, the system no longer boots. What is most likely the cause of this problem?
The correct answer is A. SCSI-1 supports only 8 devices including the adaptor.. SCSI-1 uses a 3-bit ID field, supporting exactly 8 device IDs (0-7) per bus including the host adapter, leaving a maximum of 7 usable drive slots.
Question
You ran out of space and added a eighth disk to your SCSI-1 system. When you try to start, the system no longer boots. What is most likely the cause of this problem?
Options
- ASCSI-1 supports only 8 devices including the adaptor.
- BSCSI-1 supports only 6 disks per adaptor.
- CThere is a SCSI-ID conflict that causes that problem.
- DYou forgot to set the SCSI-ID #8 for the new disk.
How the community answered
(41 responses)- A90% (37)
- B2% (1)
- C2% (1)
- D5% (2)
Why each option
SCSI-1 uses a 3-bit ID field, supporting exactly 8 device IDs (0-7) per bus including the host adapter, leaving a maximum of 7 usable drive slots.
SCSI-1 defines a 3-bit device ID space, yielding exactly 8 unique IDs (0 through 7) per bus. The host adapter itself occupies one ID, typically ID 7, which means only 7 IDs remain for attached drives. Adding an eighth disk brings the total device count to nine, exceeding the bus capacity and preventing the system from enumerating devices correctly at boot.
There is no separate 6-disk-per-adapter rule in SCSI-1; the actual physical constraint is 8 total devices per bus, including the adapter.
While SCSI ID conflicts can cause problems, the root cause here is exceeding the maximum number of supported devices on a SCSI-1 bus, not a simple ID conflict among existing devices.
SCSI-1 IDs only range from 0 to 7; ID 8 does not exist within the SCSI-1 addressing scheme, so it cannot be assigned to any device.
Concept tested: SCSI-1 bus device limit and ID addressing
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