How much slower would a full SSD get?

nr0003

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Jul 22, 2017
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People say that you should leave 20% of your storage free on an SSD. But with some SSDs that's a lot. For example, if you had a 250gb it would only be 50 GB but if you had a 1TB that would be 200 GB so I was wondering how slow would it make the SSD if I filled it all the way up? Would it slow down to the point that HDDs would be faster than them?
 
Solution
Reads would still be fast, but writes would be VERY slow. 50% speed hit wouldn't be unexpected. Some disks had a firmware bug that slowed them when they reached 50% full.