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Defrag Hard Drive in Windows to Improve Computer Performance

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    When searching how to improve hard disk performance or computer performance on the internet, users are always suggested defragging hard drive. Well then, what is hard disk defragmentation? How does fragment appear on hard disk? How does disk defragmentation improve hard drive or computer performance? How to make effective disk defragmentation? Maybe, some of you have great understanding of one or more questions, but most people just know little or even nothing about hard drive defragmentation. Therefore, we compose this post by answering these questions one after another.

    What Is Disk Defragmentation

    Defragmentation is much related to file systems on electromechanical disk drives, and it is the process of picking up all pieces of data which spreads across a partition (it is also called volume) and then putting these pieces together. Maybe it is difficult for some people to clearly know the very process just after seeing the description, so next let’s see a specific example.

    Suppose: there are 10 clusters in one partition, and a file uses the first, the third, and the ninth cluster since one cluster cannot hold all content of the file, like this:

    fragments on hard disk drive

    That is to say File 1 consists of 3 pieces, and each cluster hold one piece. Disk defragmentation is the process of putting these 3 pieces of data together so as to make a file saved in continuous space, as the following picture shows:

    defrag hard disk drive

    Now users would know how defragmentation works. But at this time some users may ask why a file could be saved to several different locations on a drive rather than stored in one place. Actually, this is our second question how fragments are generated. Let’s see the following explanation.

    How Fragments Emerge

    Generally, when we are saving files to a new partition or volume, all files will be saved continuously, for example:

    save files continuously

    However, after one of these files is deleted, for instance File 3 is deleted, space occupied by this file will be marked available for new files, and file system can save any new file to the newly released space even if there is unused space left at the end of the drive (file system just allocates space at random). Supposing File 3 releases 2MB space but a 3MB file will be saved to the released 2MB space, what will happen? Definitely, space released by File 3 cannot hold all content of the new file, and file system has to allocate more space for this file from other released space or unused space. Thus we may get the following result:

    The new file is made up of 2 parts: one is after File 2, and the other is after File 5. Under this situation, we say data fragments are generated.

    how fragments appear

    Actually, apart from deleting and writing operation, editing or modifying an old file may cause fragments. For example, the original size of File 1 is 20MB, but then we added some content to this file, making it 30MB now. That is to say extra 10MB space is required. At this time, if there is no free space available after File 1, file system needs to allocate 10MB unused space from other places for the added content, which means File 1 will spread across the drive and data fragments are generated, too.

    Once fragments reach to certain degree, users need to defrag the disk. If not, hard disk performance would be affected largely. So let’s turn to the third question.

    How Does Disk Defragmentation Improve Computer Performance (Benefits)

    There are lots of benefits to make disk defragmentation, and in this post we just list major 3.

    1.Decrease Data Access Time Largely (speed up computer)

    As we know, all files saved on a hard disk (here we refer to mechanical hard disk rather than SSD) are accessed via magnetic head. If a file consists of multiple fragments, the hard disk (especially magnetic head of the disk) will do much extra work. To be specific, when we are accessing a file which is saved in 2 or more different locations, the head needs to move here and there so as to read all fragments of the file, thus increasing seek time. However, after defragmentation, all pieces of the file will be gathered to one extent so that the head only needs to work in one extent. Naturally, our computer would run much more quickly since a lot of seek time are reduced. In addition, defragmentation helps the most when it comes to startup times. Therefore, speeding up computer is the biggest improvement brought by defragmentation.

    2.Expand Hard Disk Service Time to a Large Extent

    We have said the magnetic head should move here and there to read a fragmented data. That is to say, if there are a slew of fragmented data saved on a volume or partition, the head needs to do much more movements. With reading and writing data frequently, our hard disk may be physically damaged after a long time. That is to say its service time could be reduced. However, if we are doing defragmentation on the volume at this time, read-write operation will be reduced largely since all fragmented files will be rearranged and reunited. In other words, hard disk service time could be increased.

    Then, let’s go to the third improvement or benefit.

    3.Make It Much Easier to Perform Disk and Partition Management

    In order to make full use of hard disk space and optimize disk performance, many users plan to do disk and partition management, such as extend small partition, change cluster size, convert file system, check file system, and merge partition. However, if they make management on disk or partition which is with lots of fragmented files, they may receive different types of errors. For example, the partitioning program (either Windows built-in or third party) crashes suddenly. Therefore, before doing partition-related operations (especially making relatively complex operations), users had better defrag the hard disk or volume in advance.

    Tip: Windows snap-in Disk Management tool always fails to do some complex or advanced operations, for instance it cannot enlarge a partition when there is no contiguous unallocated or free space on the right side. So here we suggest using free but wonderful third party partitioning program like MiniTool Partition Wizard Free to do partitioning. If you haven’t found a satisfying tool, just have a try.

    Now that defragmentation will bring us big benefits, how can we do this task? Next, we are going to take Windows 7 for example to show users detailed steps.

    How to Defrag in Windows 7

    Tip: SSD users had better not do defragmentation, because it doesn’t do any help and even reduces the life of SSD. And this is only recommended for HDD users.

    To do defragmentation, users need the help of disk defragmenter, and they can use either Windows built-in Disk Defragmenter or third party programs. Here, we just recommend Windows snap-in program since this tool is powerful enough to do the operation.

    But before doing the defragmentation, users should pay some attention to the following notes:
    1.Do not run any program and shut down all autorun apps during defragmentation.
    When we are making defragmentation, the hard disk will be running at a high speed. If we read or write data at this time, our computer may crash or the entire hard disk may be physically damaged.
    2.Do not do defragmentation frequently
    Defragmentation is much different from other computer operations since the former will make the hard disk spin at a high speed. If users defrag hard disk frequently (operate hard disk frequently), the service time could be reduced rather than increased. Therefore, it is highly suggested that users do defragmentation when necessary. Tip: they can analyze disk to see whether defrag is needed or not.
    3.Had better not defrag the partition which saves system backup.
    If users make defragmentation for partitions which stores system backup, the backup might be useless.

    After knowing these 3 aspects, users need to activate the program by doing the following operations: click Start button, type disk defragmenter in the search box, and run Disk Defragmenter as administrator. After these operations, we will get the following window:

    disk defragmenter main interface

    Windows built-in Disk Defragmenter provides users with 2 options to defrag a hard drive: run disk defragmenter on a schedule or run manually. If you just want to let the program run at a scheduled time, choose “Turn on schedule…”.

    configure disk defragmenter schedule

    Then, check the box of “Run on a schedule”, configure defragmentation Frequency/Day/Time, choose disks or drives to defrag, and finally click “OK” to confirm operations.

    Of course, we can also run this program manually every time we want to defrag a drive:
    • Select the partition or volume we want to defrag under Current status.
    • Click Analyze disk to determine whether the drive needs to be defragmented.
    • Tap on Defragment disk.


    Disk defragmentation may take from several minutes to a few hours, which depends on the size and degree of fragments on your volume. However, in order to help users run Disk Defragmenter better, we are showing the following tips:
    1.Only partitions that can be defragmented are shown under Current status. If the partition you want to defrag is not shown there, it might contain errors. Under this situation, please try to repair the partition at first, and then redo defragmentation. For how to repair a volume, please doing like this: open Computer, right click the partition which may include errors, select Properties, and choose “Check now” under Tools tab.

    2.After the analyzing is finished, we can see the percentage of the fragments on the selected drive under the Last Run column. If the number is above 10%, users are suggested to defragment the disk. Of course, when the number is below 10%, users can also defrag the drive, but 10% is the recommended value.

    3.If Analyze disk doesn’t work in normal boot, users can try starting computer via Safe Mode: press on F8 when starting computer and then highlight Safe Mode.

    4.Windows Disk Defragmenter can only defrag the partition which is formatted with NTFS, FAT, or FAT32.

    5.Disk Defragmenter may fail to work when there is less than 15% free space left in the target partition. If users want to do defragmentation under this situation, there are 3 choices available: delete some useless files, transfer a part of files to another drive, and enlarge the target partition. It is believed that almost all users know how to delete a file, but what if all files in this partition are needed or deleting needless files only releases little space? Actually, under this situation users can try extending the partition by taking free space from other partitions on the same disk though defragmentation had better be made before extending.

    Are you feeling it much slower to access a file? Or do you delete, write, and edit files frequently on a drive? Now you can try using Windows Disk Defragmenter to analyze data fragments on your drive, and then make defragmentation depending on the analyzing results. However, if you are unwilling to use program Windows provides, third party utilities are also OK. Currently, Defraggler (free), MyDefrag (free), and Smart Defrag (free) are proved to be available. But to sum up, no matter which program you are going to use, pay close attention to notes and tips introduced in this post, which may become keys to success.