Storage Systems

What are File Allocation Methods in an OS?

File allocation methods are the strategies a file system uses to map a file’s logical blocks onto physical disk blocks, and the three classic approaches are co…

What are Directory Structure Types in an OS?

Directory structure types describe how a file system organizes the mapping from file names to files, and the main forms are single-level, two-level, tree-struc…

What is FCFS Disk Scheduling?

First-Come-First-Served (FCFS) disk scheduling services disk I/O requests in the exact order they arrive in the queue, moving the disk head to each requested c…

What is SSTF Disk Scheduling?

Shortest-Seek-Time-First (SSTF) disk scheduling always services the pending request whose cylinder is closest to the disk head’s current position, greedily min…

What is SCAN Disk Scheduling?

SCAN disk scheduling moves the disk head in one direction across the disk, servicing every pending request it passes along the way, until it reaches the far ed…

What are the Basics of Disk Structure?

A traditional hard disk is organized into platters divided into concentric tracks, tracks divided into sectors, and matching tracks across all platter surfaces…

SSD Scheduling Considerations vs Hard Disks

Because SSDs have no moving read/write head, seek-minimizing algorithms like SCAN or SSTF give little benefit and can even hurt performance, so OS I/O schedule…

What is File System Consistency Checking (fsck)?

File system consistency checking is the process of scanning on-disk metadata — inodes, directory entries, block bitmaps, and free lists — after an unclean shut…

What is a Log-Structured File System?

A log-structured file system treats the entire disk as a single sequential append-only log, buffering all writes — data and metadata alike — into large segment…