Defragmentation

Defragmentation is the process of reorganizing data on a storage device so that the pieces of a file are stored in adjacent physical locations. The goal is to reduce fragmentation, which occurs when file blocks are scattered across the disk. Fragmentation can increase seek times and slow down data access, especially as files are created, modified, or deleted over time.

Defragmentation software analyzes the file system, moves blocks to create contiguous sequences, and consolidates free space to reduce future fragmentation. The operation may require temporary storage and multiple read/write passes, and it updates the file system metadata. On traditional hard disk drives, defragmentation can improve sequential read/write performance and reduce average access time for heavily used systems.

On solid-state drives, defragmentation is typically less beneficial and can cause unnecessary wear since SSDs access data without physical seek. Modern operating systems generally avoid routine defragmentation of SSDs, relying on TRIM and wear-leveling instead. Some tools offer defragmentation-like options for SSDs, but they are usually discouraged.

Memory defragmentation is a related but separate concept in which an operating system or allocator compacts free memory to reduce fragmentation of available space. This approach differs from disk defragmentation and uses different techniques, such as compaction or relocation of allocations during low-memory periods. Overall, defragmentation aims to improve performance and space utilization, with applicability depending on the storage medium and workload.