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I fail to see how defrag makes any sense at all for SSDs. Unless by "defrag" they mean TRIM and other optimizations which can be useful for SSDs. True defrag of course makes sense for spinning HDDs. But don't listen to me, see what Crucial has to say about itYes, with SSDs it is highly recommended to not turn off the Scheduled optimization in Defragment and Optimize Drives ("%WinDir%\System32\dfrgui.exe") except if you have installed, e.g., Condusiv DymaxIO which will turn off that option automatically for SSDs when DymaxIO's own SSD optimization technology takes over from it. (Similarly, DymaxIO also turns off the scheduled defrag for HDDs when its own HDD optimization technology takes over from it.)
The scheduled optimization that Windows' Disk Optimization uses to optimize SSDs is different from the one that it uses to defrag HDDs. However, the scheduled SSD optimization does include a (partial) defrag that is performed only after it detects that fragmentation has piled up beyond a certain threshold [that is a lot higher than the threshold that it uses to handle HDDs]. Additionally, the scheduled SSD optimization performs a retrim, as TRIM commands can sometimes be performed by the SSD controller in such a way that no real action is taken by it, i.e. during those times when the SSD controller's total workload is too heavy to keep up with performance. So, the purpose of a retrim is just to send the same TRIM commands again, i.e. during those times when the SSD controller's total workload can be expected to remain lower for a period of time that will hopefully be long enough for the controller to take the desired actions after all. But TRIM (and retrim) is not a defrag so, it begs the question, why is a partial defrag still needed with SSDs.
The reason why a partial defrag [that, like I said, Windows performs on SSDs automatically by default] is still needed with SSDs is as follows.
Firstly, when fragmentation piles up beyond a certain level, both SSD performance and SSD life expectancy start to plummet steeply. Just the level/magnitude [of fragmentation] at which performance and life expectancy start to degrade with SSDs [in such a way that can be noticed] is a lot higher when compared to HDDs, and, the impact on life expectancy with HDDs is negligible (or almost), whereas the impact on performance with HDDs can become noticeable even with just a moderate amount of fragmentation. Also with HDDs, if fragmentation keeps building up, the loss in performance worsens much earlier on, but the claim that severe fragmentation buildup cannnot hurt SSDs is still false, even though there will always be those who keep believing that it's true (i.e., flat earthers).
Secondly, the NTFS filesystem has a maximum limit on the number of fragments that it can cope with. In spite of the fact that this maximum number is very high, good reasons to assume that it can never be reached with SSDs are pretty rare. If it gets reached, the NTFS partition will almost certainly suffer permanent data loss, and possibly even suffer complete permanent data loss. Windows has no built-in mechanism to check nor warns you up front. The risk may be small, but the consequence might not be small. So, keep the scheduled optimization turned on. Or if you prefer to run the risk of later regretting that you turned it off, then turn it off.
Should You Defrag an SSD?
There are many questions around whether to defrag an SSD. Head to Crucial for expert advice on solid state drives and whether defragmentation is necessary.
www.crucial.com
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