How much free space to leave on a HDD/SSD?

Discussion in 'iMac' started by iMas70, Nov 3, 2018.

  1. iMas70 macrumors 65816

    Sep 4, 2012
    I know it's not good to have a drive that is totally full. How much free space should be left? And does that matter if it's a HDD or SSD?
  2. nambuccaheadsau macrumors 68000


    Oct 19, 2007
    Nambucca Heads Australia
  3. mikehalloran macrumors 65816

    Oct 14, 2018
    The Sillie Con Valley
    The short, simple answer:

    SSDs have the manufacture’s recommended free space built in. It’s called provisioning or over-provisioning and is controlled by the drive’s firmware. With the Samsung 850 EVO up, it’s 8% set aside for provisioning. Other, newer SSDs are running about the same.

    Older SSDs have more but with garbage collection and TRIM, that much space is no longer considered necessary. This is why you’ll see a capacity of 960GB on one SSD and 1000GB on another, both rated 1T and built with 1024 (more or less). You can allow more if you disagree with the maker of the drive.

    HDDs run slower as you approach capacity. 15% is the recommended free space to avoid this.
  4. Fishrrman macrumors P6


    Feb 20, 2009
    For a boot drive, you'd want some free space on it for things like the VM swap file, temp files for apps, etc. Mr. Halloran explained that well in the post above.

    If the drive IS NOT used as a boot drive, but for data storage only, I'll guess that one can just about "fill it up" to "the max". You'd still want -some- free space available (I'd guess about 1-2% of total capacity)...

Share This Page

3 November 3, 2018