Should using disk defragmenter clear up or reduce free space on a hard-drive?

[Fuzzball]

I have a laptop with SSD C: drive and 750GB HDD D: drive. I recently found that on the D: drive and also an external HDD (F: ) I have, there was less free space than there should be. If I added up the amount of GB my files were using, it came to less than what my computer says the D: and F: drives are each using. I think in the end what's using up my space on D: is system restore points, which I'm going to turn off, but why the F: drive has less space than it should is still a mystery.

One of the things I tried to free up space was using the disk defragmenter. Don't worry, I didn't use it on my SSD! When I tried it on D: I ended up stopping the process half-way through because it was late in the evening and it was taking a long time. This seemed to reduce the free space by a few GB! But when I then went and did the defrag process again and let it go all the way through, it ended up with more free space than I'd started with. Good.

However, when I tried disk defrag on the external HDD, at the end of the process it had lost free space! About 50GB! What happened there? I'm I not supposed to use disk defrag on external HDDs?

So what is disk defragmentation meant to do? Is it meant to increase or decrease the amount of free space you have on a drive?

 

[Tom DWC]

Essentially all disk defrag does is move all of the big chunks of files that are scattered across the hard drive into one adjoining segment, increasing the read speed of the drive. It will never greatly improve performance, especially on faster drives. (Which is why it's disabled on SSDs because the read speeds are so fast anyway and it would reduce their usable life.)

What it doesn't set out to do is make more space or indeed decrease it, though increased performance can be at the expense of space - and it's performance driven.

So a few GB movement either way as is the case with your D drive sounds normal - a 50GB reduction on the external is not. I recommend installing i.disk to get an exact picture of where all the space is going.

 

[Fuzzball]

So a few GB movement either way as is the case with your D drive sounds normal - a 50GB reduction on the external is not. I recommend installing i.disk to get an exact picture of where all the space is going.

Well I'm really not sure what's going on with that external hard-drive. I just used the WinDirStat program (which someone on this forum suggested before) to look up how much disk space is being used up on my drives, and it says there's only around 483GB total on the external HDD, when written on the device itself it says 1TB! Half the free space is missing!? Very weird.

 

[ubuysa]

The built-in Windows defrag tool only ensures that files are contiguous, it does not defrag free space (ie. it does not move files around to get all the free space in one lump). So what you are seeing after the defrag is fragmented free space.

It is very sensible to move files around to get all the free space in one lump, sadly the Windows defrag tool can't do that. Give Ultimate Defrag a try (http://disktrix.com/). It's not free but it's not expensive either and it does a superb job because it's an optimising defragger. You can place your high performance files (those you use a lot) on the faster outer tracks (close to the MFT, which you can also place wherever you want) and your rarely used data on the slower inner tracks with the free space in one lump between the two. I have used it for many years on several HDD only laptops and PCs and it makes a world of difference to performance.