Do I need to defrag Windows 10?

De-fragmentation of a SSD is useless by design. Fragmentation is only an issue of HDDs where the reading/writing head has to move all over the disks in order to "collect" the different parts that together build your data (e.g. the audio files of an album). De-fragmentation does the following: It "collects" the different parts of your data and rearranges them so they are stored subsequently on the disks meaning the head does not have to move that much in order to read out the data which leads to faster reading speeds.

For an SSD on the other hand fragmentation is not an issue. It reads fragmented data just as fast as not fragmented data. So besides reducing the SSD's lifetime de-fragmentation would also be completely useless.

SSD's have another issue though. They can write onto the entire storage but they can only delete entire blocks (can't remember the exact details right now but you can google it, just look up trim on Wikipedia). That's what trim is for. So what happens is with time there are a lot of incomplete blocks on your SSD, partially filled with valid data, partially filled with data marked for deletion. But that data cannot be physically deleted because the blocks still contain valid data. Now trim comes into play and rearranges the data so all the valid data is stored in a way it fills up as much entire blocks as possible, leading to the "marked for deletion" data also filling up entire blocks. And now those entire blocks can finally be physically deleted making room for new data.

In short words: De-fragmentation of SSDs does nothing useful but (in theory) destroys your drive.

On HDDs, some of what may appear to be fragmentation is by design. Some programs (MS Office, data bases etc.) leave empty blocks at the end of data files so those files could be expanded linearly and so speed up their loading and writing to. Windows usually report less of fragmentation than other, third party defrag programs because partly of that.

altae said:

...For an SSD on the other hand fragmentation is not an issue. It reads fragmented data just as fast as not fragmented data. So besides reducing the SSD's lifetime de-fragmentation would also be completely useless. ...

But, as has been discussed earlier in the thread, it's not as simple as that: http://www.hanselman.com/blog/TheRea...ntYourSSD.aspx

EXCERPT -
...Storage Optimizer will defrag an SSD once a month if volume snapshots are enabled. This is by design and necessary due to slow volsnap copy on write performance on fragmented SSD volumes. It’s also somewhat of a misconception that fragmentation is not a problem on SSDs. If an SSD gets too fragmented you can hit maximum file fragmentation (when the metadata can’t represent any more file fragments) which will result in errors when you try to write/extend a file. Furthermore, more file fragments means more metadata to process while reading/writing a file, which can lead to slower performance....

altae said:

...In short words: De-fragmentation of SSDs does nothing useful but (in theory) destroys your drive.

I think we need to draw a finer distinction on this thinking, that's exactly why "defrag" and SSD in the same sentence seems so inflammatory.

Word Man said:

But, as has been discussed earlier in the thread, it's not as simple as that: http://www.hanselman.com/blog/TheRea...ntYourSSD.aspx

I think we need to draw a finer distinction on this thinking, that's exactly why "defrag" and SSD in the same sentence seems so inflammatory.

I think it's more down to comparing defragmentation on mechanical HDDs and SSDs, it's not the same thing.

CountMike said:

I think it's more down to comparing defragmentation on mechanical HDDs and SSDs, it's not the same thing.

Totally agreed - and also a little a bit, when it comes to what's needed for optimization side of things, newer SSDs versus older SSDs and new OS's versus older OS's.

None of that SW prevents fragmentation. I run HDD speed tests before and after defrag with few programs (not on my disks) and there was no difference, not since W7 that doesn't fragment disks even after long usage, several years with heavy traffic in my case. Most I have seen was 1 - 2% according to Windows defragmenter. Auto defragment turned off.