Final answer:
The controller in SCSI disks used in high end PCs maintains a list of bad blocks on the disk. The disk is initialized during low level formatting, which sets aside spare sectors not visible to the operating system.
Step-by-step explanation:
In SCSI disks used in high end PCs, the controller maintains a list of bad blocks on the disk. The disk is initialized during low level formatting which sets aside spare sectors not visible to the operating system.