What does disk defragmentation accomplish on a hard drive?

Disk defragmentation primarily focuses on optimizing the arrangement of data on a hard drive. Over time, as files are created, modified, and deleted, data can become fragmented, meaning that the parts of a single file may be scattered across different physical locations on the disk. This fragmentation can result in slower read and write times, as the disk's read/write head has to move to various locations to access the parts of a file.

By performing disk defragmentation, the operating system rearranges these fragments and stores files in contiguous locations. This improves the efficiency with which data can be read and written, thus enhancing overall system performance. When files are stored sequentially, the read/write head has less distance to cover, leading to faster data access speeds and reduced load times for applications and files.

This understanding highlights the importance of maintaining an organized data structure on traditional hard disk drives (HDDs), whereas solid-state drives (SSDs) do not have the same requirement due to their different architecture. Therefore, the correct answer emphasizes the primary goal of disk defragmentation: to optimize data placement for improved performance.