HDD/SSD "overhead"

elf69

macrumors 68020
Original poster
Jun 2, 2016
2,333
487
Cornwall UK
Does mac need minimum 10-20% free disc space on primary drive like a windows system does?

I seen many windows machine crawl or die due to lack of this overhead.

I ask as i'm going fit a small ssd to my imac and wounder if it be too small.

At present if I remove all my files from home folder will only need 29GB on primary.
Going to fit a 64GB SSD.

also got photoshop and dreamweaver to install yet.
 

DeltaMac

macrumors G4
Jul 30, 2003
10,470
2,788
Delaware
64GB? too small, unless you have a good plan using external drives for scratch and caches - and watch your internal space cautiously.
Photoshop? That doesn't help you at all, if you have space issues.
I still apply the same free space criteria that I have used as a rule of thumb for years.
Never allow free space less than 10% of the total drive space. I also allow space for 50% more than the RAM that is installed in the system.
So, with 64GB capacity on one volume, and it's your boot drive, assuming 8GB of RAM installed. Your free space should not drop below ~18GB.
note: that's my standard, perhaps not a provable technical answer, just how I work...
 

elf69

macrumors 68020
Original poster
Jun 2, 2016
2,333
487
Cornwall UK
6GB ram (maxed out)

using 500GB in optical bay for my home folder.

So maybe look to by a 120GB then...
 

kschendel

macrumors 65816
Dec 9, 2014
1,062
335
SSD's don't like to be full. So yes, allow roughly 20-30%, and I think you're really pushing your luck with only 64 Gb. I'd move up to 128 Gb.

Another thing to consider is the space overhead needed for a system upgrade. If your base system is ~30 Gb, a major point update might need a considerable fraction of that temporarily. Add internal filesystem overhead and you're perilously close to not being able to update your system with the 64 Gb unit.
 

dwig

macrumors 6502a
Jan 4, 2015
696
280
Key West FL
SSD's don't like to be full. So yes, allow roughly 20-30%, and I think you're really pushing your luck with only 64 Gb. I'd move up to 128 Gb.

Another thing to consider is the space overhead needed for a system upgrade. If your base system is ~30 Gb, a major point update might need a considerable fraction of that temporarily. Add internal filesystem overhead and you're perilously close to not being able to update your system with the 64 Gb unit.

+1

My iMac at work is configured to have only apps, configuration files, temp files, and very very few user files on its internal SSD. All "data" files are placed on externals. I have Ps, Lr, Dw, Id, Br, Ai, and Acrobat from the Adobe CC suite installed along with a few basics (the Apple "shovelware", Firefox, Chrome, FileZilla, and a few other small utilities. All of this, plus the OS, take up about 64gb.

I would think that if you are going to use a machine for anything more than email and web browsing, you would want more than 64gb. Even my little Windows 10 tablet's little 32gb primary storage is extremely marginal for such tasks. It took a secondary interanal 32gb to make it really functional, though I've now boosted that to 64gb.
 

ckelley

macrumors regular
Aug 25, 2003
130
171
Austin, TX
Any particular reason for using such a small drive, or is it one you just have around you want to put to use? You can get a 500GB Samsung 850 EVO drive for ~$170. You should have at minimum your system folder and all Applications on the SSD to take advantage of its speed.
 
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elf69

macrumors 68020
Original poster
Jun 2, 2016
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487
Cornwall UK
yeah the 64GB SSD was free and laying in drawer.

Thought might speed up my aging imac.

but will get a 120GB and a 500GB HDD in optical bay for data, and a 1TB USB for time machine.
 

T'hain Esh Kelch

macrumors 603
Aug 5, 2001
5,181
4,751
Denmark
The 10-20% number is back from when harddrives were much smaller. In my personal experience, you'll need 10-15GB free space in order not to feel any impact on speed. This is without running some pro app that creates a scratch disk of course.
 
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