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Hello! I currently have about 50GB of free space on my SSD, but I was thinking of leaving around 10GB left for Mac OS X...is that too little? I have a 256GB SSD...:confused:

As a general rule, it's a good idea to leave around 10% of your drive free, more if possible.
 
For maximum performance you should have at least 10% free or better up to 20%.
 
The ol' 10% rule doesn't really apply to today's larger drives. There are 2 things to consider with ssd drives: virtual memory and garbage collection.

Check your page outs in the memory pane of activity monitor. If the number is big, you need to install more ram as you're running low on memory and this is causing a lot of unnecessary writes to your drive.

Ssd drives depend on garbage collection routines (trim, etc.) to erase the flash memory in unused blocks. This happens at idle. If enough free blocks are not erased, it will dramatically slow down write times.

So it really depends on your work flow as to how much free space is enough. If you're regularly working with large files like video, 10GB is probably not enough. If your usage is simple documents like word processing files and spreadsheets, 10GB will be plenty to support these and the various system overhead such as cache files.

HTH
 
I don't understand this "leave 10%" rule of thumb. Has it been factually proven with the SSD? Specifically the PCIe SSD in 2013 Airs? Or is it just a myth that has grown to legend?
 
I don't understand this "leave 10%" rule of thumb. Has it been factually proven with the SSD? Specifically the PCIe SSD in 2013 Airs? Or is it just a myth that has grown to legend?

The 10% is not a hard and fast rule, but rather a general estimate. Performance can be reduced if a drive is too full, as there needs to be free space for growing logs, caches, user files, paging, etc. Obviously, if the drive is larger, such as 1TB, the percentage can be somewhat smaller. The point is, it's not a good idea to fill up the drive.
 
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I also have a 256 SSD.

Recently via About This Mac>Storage, it said I had about 20-ish gigs left.
Then I started getting messages at startup saying I only had 13gb left.

Today, Apple>Storage says I have 29gb free, whereas I went to Disc Utility and it says I only have 21gb free.

I’m guessing the latter is where I should go to find out the true amount of space left?
 
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