The following SCSI devices are attached to CALFLT:
| SCSI Id | Device Name | Device Description |
| 0 | $101$DKA0: | Primary System and CFLT code disk |
| 1 | $101$DKA100: | Secondary, shadow copy of system and CFLT code disk |
| n/a | DSA0: | Logical device for system and CFLT code disk shadow set |
| 3 | CALFLT$MKA300: | 4mm tape drive |
| 6 | CALFLT$GKA60n: where n=0...7 | TR801 SCSI Transputer Interface |
| 7 | n/a | System SCSI controller |
In order for CALFLT to boot, the TR801 tranpsuter interface must be powered OFF. If the TR801 is on, the system will try to serve the device to the cluster and will fail booting. After the system has booted, the TR801 may be turned on and used.
Each of the above devices uses the internal SCSI chain. The tape and disk drives are located physically inside the CPU box and take their power from the CPU box's own supply. The TR801 is located outside the CPU box in its own housing with its own power supply. The length of the SCSI chain is strictly limited, requiring the cable attaching the TR801 to be very short, thus requiring the delicate connection from the internal CPU box SCSI cable directly to the TR801 motherboard. To help avoid ground shifts along the SCSI bus, it is best to use adjacent 220V outlets on the same circuit for the CPU box and the TR801.
NB: The CPU box also has an external SCSI outlet for the same SCSI bus chain. The TR801 often will not function reliably, or at all, when using this external outlet.
The two disks $101$DKA0 and $101$DKA100 form a VMS System Shadow Set. If one of the disks fails, the other should be able to boot CALFLT and run by itself. Each disk contains a complete copy of the other disk for emergency situations. For more information on booting CALFLT in such an emergency, see the link Emergency Boots of CALFLT.
NB: The presence of the shadow set does not eliminate the need for regular archival backups of the disk using the CALFLT$MKA300 tape drive.
The individual member disks of the shadow set should never be referenced directly. Always use the device name DSA0: when referring to the disk shadow set.