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Hassie

Is defraggler really efficient in the algorithm?

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Hello all,

 

As a first time user I was surprised to see how it works.

I read that it is supposed to be a single pass algorithm.

I tried to defragment a 3T disk 50% occupied.

At first DF moved all files to the upper part of the chart,

but that included all fragmented files too.

I even noticed that the fragmentation increased in the process!

Then, after many, many hours at 99% and 1 minute to go,

fragmented files were copied again to turn from red to blue.

But when the process finally was done, after another few hours,

I was left with 0% fragmentation, but many holes of free space,

so now I am doing a free space defragment.

 

So to me it feels like a 3-pass operation and files are copied three times.

Which costs obviously an enormous amount of time,

and a severe impact on the drive's heads, because the reading and writing is done on the same drive with bits and pieces.

Also I did not see much use of the memory, I have 16G, so a m2ts file of say 9G for instance completely fits in memory.

 

Quote from this site:

 

What Defraggler does

Defraggler scans the hard drive for folders and files that are scattered in non-contiguous clusters (clusters that aren't right next to each other).

Using a single-pass algorithm, it designs an optimum layout for these files so that Windows will spend the least amount of time retrieving them in the future.

Finally, Defraggler moves the files into this optimum pattern.

 

In my opinion the optimum pattern could have been achieved by directly placing the files without fragmentation in the right place,

and without leaving holes of free space. 

 

Any other thoughts about this?

 

Greetz Hassie

 

 

 

 

 

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Sometimes the "holes" we'll see after a defrag software finishes can be files that can't be moved, files having a huge gap because of the MFT Reserve Zone being in the way.

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Thanks for your answer.

In the meantime I did some research on the disk, after a defrag free space didn't do much.

There were a lot of strange blocks that were empty. Probably they got in the way as you say...

Do not know how these were created.

So I emptied the disk, deleted the partition and formatted.

Now they are gone, I only have a light blue block, the first one, and the ninth is a purple one, the metadata, guess that's OK now.

 

So I will try DF on another disk and see how that goes... :-)

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Don't beat yourself up on what a defrag software does. Of course we the users would like to see our files all tightly packed together, however that's not necessarily the end result.

 

The gaps that are left behind may be later filled however that's based upon the defrag software's own accord of what it will or won't do during a particular run. Although better filling of the gaps may be achievable after a system restart such as if Windows will move the MFT Reserved Space -- but don't always count upon it, and it isn't always necessarily worth the time involved and stress upon the hard disk(s).

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Thanks again, I understand,

I don't beat myself up, just interested in how software works :-)

btw I have lots of disks with data and want to have them filled nicely,

because it is better for the heads if you copy and delete a lot, not for speed...

for Windows I use SSD's.

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Well, next disk went OK!

From all the disks I have, I unluckily chose the one with problems,

I now understand what happened, because all of the strange 0 byte blocks, presumably not removable,

DF could not place the big files at the top without fragmentation.

After that DF went on defragmenting and put the big files "lower" not fragmented while leaving a lot of holes of free space...

The second disk all went well in one go, all blue at the top.

So the algorithm is OK, assumed the disk is OK :-)

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