What is the primary purpose of disk defragmentation?

The primary purpose of disk defragmentation is to organize fragmented data for improved performance. Over time, files on a hard drive can become fragmented, meaning that parts of a single file are stored in non-contiguous sectors across the disk. This fragmentation can lead to slower access times, as the read/write head of the hard drive has to move around more to access all the parts of a file.

When defragmentation is performed, the disk utility reorganizes the data so that files are stored in contiguous blocks, which minimizes the movement required by the read/write head. As a result, this leads to faster file access and improved overall system performance. Defragmentation helps in efficiently using the storage space on a hard disk, which can be particularly beneficial for traditional spinning hard drives.

The other options refer to different functions that do not relate to defragmentation. Deleting unused files deals with free space management but does not address the efficiency of data retrieval. Encrypting data focuses on securing information rather than organizing it. Upgrading hard drive storage capacity relates to physical changes in hardware, which is outside the scope of what defragmentation achieves.