CST 334 Week 7

The first topic I learned about this week was how devices connect to the computer system. In modern computer architecture, devices such as external storage devices, keyboards and monitors connect to the CPU via an IO chip. Each device that connects to the system provides an interface, allowing the system software to interact with it. This interaction between the device and system can also be improved by Interrupt based techniques or direct memory access.

This topic led to my introduction into hard disk drives. These are rotating disks that store data in tracks by inducing magnetic changes. Writes and reads to the disk are performed by the disk head that is attached to a disk arm. Work loads can be sequential (data manipulated is in consecutive sectors) or they can be random (data being manipulated is in scattered locations across the disk). Disk scheduling (SCAN, SPTF, and SSTF) greatly impacts the cost of IO, but unlike process scheduling, it is easier to estimate the length of execution. To increase the performance of the disk, computer systems can instead use multiple disks in RAID storage. By using multiple disks in parallel, the performance, capacity, and the reliability of disk memory is improved. I also learned about several common types of RAID including how they function, along with the RAID levels advantages and disadvantages.

The last topic I learned about this week is files and directories. Files are an array of bytes that is identified by the file system by an inode number. Files are contained in directories as tuples (user readable name, inode number). Directories have an inode number as well and contain a list of files or other directories within it. It also contains a reference to itself and a reference to its parent directory.