Physical Disks

The last type of physical device we are going to talk about is physical disks. Physical disks are critical parts of any network operation, simply because without physical disks, we would have no method of storing large amounts of data and running complex programs, such as Windows Server 2003. A physical disk needs to be installed and formatted before data can be written and stored to the disk. Windows Server 2003 supports both SCSI and IDE hard drives of various sizes. While the differences between SCSI and IDE are not tremendously important for the exam, a brief explanation of both is presented here. What is important to know for the exam is the method used to number physical hard drives, and how to install and manage the physical disks, including tasks such as creating volumes, formatting volumes, and creating fault-tolerant volumes. SCSI SCSI (Small Computer Systems Interface) disks are much more common in enterprise level computing than the IDE standard. SCSI drives are generally faster and more reliable than IDE drives and for those reasons are much more widely used in mission-critical servers. The second generation of SCSI devices, nicknamed Fast SCSI, can run at 15,000 rpm and support transfer rates of 20 MBps, while IDE only supports up to 7200 rpm and transfer rates of 16.7 MBps. To support SCSI drives, a separate SCSI adapter has to be installed on the motherboard. Almost no personal computers or workstations use SCSI drives, but SCSI drives are very common in enterprise-level servers and storage appliances. SCSI cards also support connecting up to 15 SCSI drives to a single controller, while IDE supports only four. SCSI drives are connected in a daisy chain configuration. IDE AT Attached (ATA), or IDE (Integrated Device Electronics) as they are more commonly referred to, are the standard most commonly used in workstations and computers, mainly because it is cheaper than SCSI, and unless multiple drives are required, the SCSI standard isn’t needed? ATA or IDE drives were originally used in IBM PC-AT computers, and become the de facto standard for the industry. A parallel IDE cable can hold two drives, and up to four drives can be connected to a single IDE dual channel controller. When connecting two hard drives to an IDE controller using the same cable, it is important to set one of the hard drives as the “master” and the other as the “slave.” This is done by setting the jumpers on the hard drive. See the manufacturer’s documentation for how to set the appropriate jumpers. Serial ATA has made some improvements over parallel ATA in the area of speed (double that of parallel ATA) and more drives per controller (up to 15).