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Does defragging too much harm my hard disk?

Question: Can defragging harm my computer? It looks like it’s a good way to improve my speed, but after a while, I’m back with 5% fragmented disk. So does defragging harm my computer? If not on single use, then on multiple uses? In fact, can it make it even slower instead or make some applications bugged? Making them crash by moving their files around?

As I’ve explained in a previous article, defragging rarely gets you to a 100% completely defragmented machine. There are a couple of different reasons why, but I’ll leave it to that article to cover that situation. The real question here is: does defragging too often harm the machine?

Absolutely not. Let’s talk about why.

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Help or harm?

From the hardware’s perspective, defragging is just another way to access the hard disk – which is almost constantly in use anyway. Quite literally, to the hard disk it simply “looks like” a program reading and writing information from and to the drive.

Defragging often doesn’t harm the drive – it’s just as if the disk were being used heavily by any application – but in the end, it may not really help that much.

Once you get to a point of being relatively defragmented, then the additional work of defragging further just isn’t worth it. As soon as you get “pretty good” defragmentation, say in that 5% range1, then your machine is going to be essentially as fast as it would if it had been perfectly defragged.

I do recommend that you defrag periodically. Windows 7 does it automatically for you once a week. That’s a fine interval if you’re setting things up for yourself.

What defragmenting does

Defragmenting will not make your computer slower. It’s point is just the opposite: it’s arranging files on the hard drive to be more efficient.

Defragmenting also won’t harm your applications. Applications don’t even know about fragmentation.

If you open an application and you access a file, the application accesses the operating system which locates the file on the hard disk. If the hard drive is defragmented the amount of time it takes for the operating system to find and load the file might be quicker than if the drive were heavily fragmented. That’s the only thing an application might “notice”.

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Footnotes & references

1: I totally made that number up, I don’t want you to use it as some kind of benchmark. Basically after you defrag your machine once with any reasonable defragmenting tool whatever results are is likely to be good enough.

10 comments on “Does defragging too much harm my hard disk?”

  1. PC World Magazine has periodically mentioned that they have done benchmark tests showing that defragging HDD’s gain very little, if any, increase in speed. When I pose the question asking for evidence of speed improvement, all I’ve ever gotten in response is “it’s only logical that it would,” and “it seems faster to me after I do” – – I can’t argue with either response, but neither of them are evidence of speed improvement.

  2. Should be an easy test.

    Turn off all defragmentation. Let it get severely fragmented.
    Time several different hard drive intensive processes to get a baseline
    Time the same processes, see if there is any improvement.
    Defragment again

    That said, I don’t bother defragmenting, but I also haven’t turned off Windows 7’s scheduled defrag either. I get more of a speed improvement when I either wipe the system and reinstall (or reimage now) or in my laptop’s case, install an SSD.

  3. If you do a Defragment every Year then you’ll be fine…Just don’t do it too often…
    My computer keeps crashing, My friend said “Do a virus scan & a infection scan” Then “Do a Defragment”

    Doing a defragment on my server’s every month….They run like brandnew…

  4. I have win7 and I have been defragging my HDs with Auslogic for the past 16 years & 4 computers. It maybe purely psychological but I feel that is makes the computer start faster and get less “bugs” during heavy usage. My present self-built computer has two very large HDs and one huge external for safe storage. No “cloud” for me – I do not trust it.
    Anyway since it does no harm and may even be somewhat beneficial, I will continue defragging merrily every other day, it takes only 5 minutes, probably because of the frequency plus top speed processors and a very large RAM.

  5. Defragmenting does no harm until you overdo it… since your laptop/computer would have a somewhat limited space, if you overdo defragmenting… your computer can get tired and since there would be nothing left to defrag then it starts to write up more (which is how it works – by moving files around for speed) and then the computer has less storage to handle defragmenting.

    An average amount of “too much” in my opinion would be multiple times a day.

    I had 3 computers in the past…. and for me the best amount to give the computer to fragment is 2 weeks… on one computer i done it every day and it’s lifetime got worse since there was nothing to defragment. my other one i done it around every month and it worked fine. i had it for a worthwhile time but i still think that my 3rd computer worked best when i defragged it every 2 weeks. i kept a reminder on a certain day (i chose saturday) every 2 weeks. I still use this computer even though its storage is limited, and for me it is working best.
    Hope i helped :)

    • “your computer can get tired and since there would be nothing left to defrag then it starts to write up more ” If you try to defrag a hard drive which doesn’t need it, it will defrag whatever little is fragmented and then end the defrag process. It won’t use up any additional free space.

    • Um…. no. Defragging an already defragged drive does not write more. The computer does not “get tired”. If you have an actual physical hard drive “overdoing it” causes no real harm. An SSD, on the other hand, should never be defragged.


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