How much free space should you leave on an SSD?

Kippa

Senior member
Dec 12, 2011
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I am aware that it is not wise to fill up an SSD to 100%. What I want to know is roughly on a 256gb SSD how much space should I realistically leave to make the drive last? 10gb? 20gb? More or less? At the moment I have 60gb of free space left on the drive.
 

BrightCandle

Diamond Member
Mar 15, 2007
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Really depends on the model of SSD. Some of them are more than capable of running near capacity without issues and some of them start to show inconsistent file write times if the drive is too full and you write too much data to them. I would say keep on putting stuff on there until you notice and actual difference in performance and back it off a little bit.

My M4 shows a noticable decrease in performance once I have less than 200GB free. At 150GB performance is actually terrible. Small writes can take 10's of seconds, the OS will lock up for periods due to the SSD locking up and its a bit of a mess. Its actually really disappointing to me that it happens with so much free space clearly still there, its just not acceptable really to be buying an SSD and finding you need to leave 40% of it free to get reasonable performance out of it. But this is an old SSD and now well known for these sorts of problems, a new generation one shouldn't show symptoms even remotely that severe nor with so much free space.
 

Essence_of_War

Platinum Member
Feb 21, 2013
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I am aware that it is not wise to fill up an SSD to 100%. What I want to know is roughly on a 256gb SSD how much space should I realistically leave to make the drive last? 10gb? 20gb? More or less? At the moment I have 60gb of free space left on the drive.

A good rule of thumb has been 15-25% over provisioning. So for a 256 GB drive, between ~40-60 free GB should be fine.