{"id":190,"date":"2025-07-18T21:00:00","date_gmt":"2025-07-18T21:00:00","guid":{"rendered":"http:\/\/auslogics.my\/en\/articles\/?p=190"},"modified":"2025-10-16T23:51:15","modified_gmt":"2025-10-16T23:51:15","slug":"defragment","status":"publish","type":"post","link":"https:\/\/www.auslogics.com\/en\/articles\/defragment\/","title":{"rendered":"What Does Defragging Do: Easy Explanation of Disk Defragmentation"},"content":{"rendered":"

Windows users still ask, \u201cWhat is defragging?\u201d in 2025, partly because HDDs are no longer the major players in modern storage.<\/p>\n

But these drives occupy a critical role as backup devices, one that requires every drive to be in tip-top shape.<\/p>\n

Defragmentation (or defragging) is one of the techniques you need to achieve that, especially if you write and delete files frequently.<\/p>\n

It helps ensure that hard disks can access files as fast as possible and speeds up the write process.<\/p>\n

At the same time, many users still have concerns and reservations about defragging hard drives, asking questions like \u201cWhen should I defrag?\u201d \u201cWhich tools should I use?\u201d \u201cHow often should I defragment my hard drive?\u201d and \u201cWhich drive should I defragment?\u201d<\/p>\n

Stick around to find answers to these questions\u2014and more.<\/p>\n

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TL;DR: Summary<\/div>\r\n\t
<\/p>\n

\ud83d\udd04 Defragmentation lines up pieces of individual files closer together on hard disk drives.<\/p>\n

\ud83e\udde9 It is deployed when file fragments are scattered across a hard disk (fragmentation).<\/p>\n

\ud83d\udc0c The system slows down when a drive is badly fragmented.<\/p>\n

\u2699\ufe0f You can run defragmentation using Windows\u2019 built-in disk defragmenter and third-party tools.<\/p>\n

\ud83d\udeab Do not defragment an SSD, as it can reduce the drive\u2019s lifespan.<\/p>\n

\u231b These programs can also help you run scheduled defragmentation.<\/p>\n

\u26a1 Once a drive is defragged, it runs faster and improves overall system performance. <\/div>\r\n<\/div>\r\n\n

What Is Disk Defragmentation?<\/h2>\n

Defragmentation is a process that Windows uses to reorganize file fragments on hard disks to allow faster read access and improve drive performance. The rearrangement brings pieces of files scattered across the drive\u2019s surface closer to undo the effects of fragmentation.<\/p>\n

I\u2019ll explain what fragmentation is and how it affects your computer to help you understand defragmentation better.<\/p>\n

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\r\n \"Fragmentation\r\n <\/div>\r\n
<\/div>\r\n<\/div>\n

How do hard disk drives work, and what causes fragmentation?<\/h3>\n

Let\u2019s start with how data is written to and read from hard disk drives.<\/p>\n

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\r\n \"IMG\"\r\n <\/div>\r\n
How HDDs work<\/div>\r\n <\/div>\r\n
<\/div>\r\n<\/div><\/strong><\/p>\n

Within every hard disk drive, there is at least one read\/write head (attached to a mechanical arm) and a spinning disk. Whenever you save or copy a new file to the HDD, the R\/W head writes the data to sectors on the hard drive, arranged in a concentric pattern. These sectors are the drive\u2019s basic storage units, and each can only contain 512 bytes.<\/p>\n

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\r\n \"Within\r\n <\/div>\r\n
<\/div>\r\n<\/div>\n
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File systems<\/a>, such as NTFS (New Technology File System) and FAT (File Allocation Table), group sectors into clusters to increase a hard drive\u2019s basic storage unit. Still, clusters have limited sizes (usually up to 60 KB), which means fragmentation can still happen. <\/div>\r\n<\/div>\n

The drive breaks up files into pieces of 512 bytes and writes these fragments sequentially across multiple sectors. Whenever the drive needs to read a file, it must locate every fragment. File access is faster when fragments are close to each other.<\/p>\n

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Before writing data to a drive\u2019s sectors, the R\/W head first creates a Master File Table (MFT)<\/a> at a marked-out section on the drive, typically at the beginning. The MFT is where file metadata is stored. This metadata tells the drive head where each file fragment is located on the disk. <\/div>\r\n<\/div>\n

If the drive is filled up, other files may be saved to the reserved MFT space, causing MFT files to be fragmented and scattered across the disk.<\/p>\n

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\r\n \"IMG\"\r\n <\/div>\r\n
How does fragmentation happen?<\/div>\r\n <\/div>\r\n
<\/div>\r\n<\/div><\/b><\/p>\n

Whenever you delete files for the first time, the spaces they originally occupied will become empty. The hard drive will then overwrite those empty spaces with new files.<\/p>\n

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\r\n \"Whenever\r\n <\/div>\r\n
<\/div>\r\n<\/div>\n

If the new files you\u2019re saving are significantly larger than the leftover empty spaces, the R\/W head will first fill up those empty spaces and then write the rest of the file fragments to other sectors on the drive.<\/p>\n

As you continue to delete files and create or copy new ones, file fragments continue to scatter across the disk. As a result, it takes the HDD head longer to read files since it must locate every fragment.<\/p>\n

The following are the effects of fragmentation:<\/p>\n