Week 31: CST 334 - Operating Systems

WK07: Weekly Learning Reflection

This week we covered several connected topics related to storage and input/output in operating systems. The main topics were I/O devices, hard disk drives, files and directories, and file system implementation. These topics helped explain how the operating system communicates with hardware and how data is stored and organized on disk.

I/O devices focused on how the OS interacts with devices like disks and keyboards. We learned about programmed I/O, interrupts, and DMA, and how each method affects CPU usage and performance. Hard disk drives built on this by explaining how physical disks work, including seek time, rotational delay, and transfer time. This helped me better understand why disk access is much slower than memory access and why performance optimizations matter.

The interlude on files and directories explained how files are organized and accessed. We learned that files are made up of data and metadata, and that directories are special files that map names to inode numbers. This connected well with file system implementation, which showed how inodes, data blocks, and free space bitmaps are used to manage storage. The distinction between file system data structures and access paths made the abstract ideas more concrete.

The topic I found hardest was file system access, especially counting disk I/Os during path resolution. I understand the general process of walking directories and reading inodes, but I still find it confusing when deciding what is assumed to be cached and what must be read from disk. The exact assumptions can change the final answer, which makes these problems tricky.

My biggest aha moment came when learning about inodes and directory entries. Realizing that filenames are not stored inside inodes but in directories helped everything click. This made file linking and file deletion much easier to understand.

These topics connect well to virtualization and to other classes like databases and systems programming. Understanding how disks and file systems work helps explain performance limits and design choices in real applications.