If I'm running a RAID 5, do I need to leave 10% of the hard drive space free?

Joined
Oct 14, 2007
Messages
408
Reaction score
0
Points
16
I know the rule of thumb for external hard drives is to keep 10% of the hard drive open. I have a RAID 5 made up of 4 4tb hard drives. Because of how RAID 5 works, I have a shade under 12 TB to play with. Can I fill that entire space or do I need to leave 10% of that 12 free?
 
C

chas_m

Guest
Actually 10 percent would be far too little in my view. If this RAID setup you have contains an operating system, then yes you need to keep lots of space free -- I would lean towards 20 percent, though "percent" is not really the right way to measure this need, it's more about how you use the computer and thus people tend to fall back on a comfortable percent because there's really no simple rule that works universally.

If you find yourself needing 12TB of storage, then I would presume you work on some big files, so your need for temp/cache/etc free space is probably way larger than a light-duty user, just as an example.

So anyway -- tl;dr version -- if you're booting off this, then yes you need to keep a substantive amount of free space available. If it's just data storage (no OS), then you can fill it right up.
 
OP
O
Joined
Oct 14, 2007
Messages
408
Reaction score
0
Points
16
I am working on a film. All my movie files are on it, but I'm running Mac OS off my laptop. So, I can fill it all up?
 
Joined
Apr 26, 2008
Messages
2,963
Reaction score
120
Points
63
Location
Belgium
Your Mac's Specs
iPad Pro 12.9 latest iOS
Actually no, you need a little free space but not the 10% :)
You can fill it " almost " all up ....
You don't need to worry about your OS giving up on you when that disk is full, but give it a little breathing space. Some of my external disks are at 1% free space :)

Cheers ... McBie
 

bobtomay

,
Retired Staff
Joined
Dec 22, 2006
Messages
26,561
Reaction score
677
Points
113
Location
Texas, where else?
Your Mac's Specs
15" MBP '06 2.33 C2D 4GB 10.7; 13" MBA '14 1.8 i7 8GB 10.11; 21" iMac '13 2.9 i5 8GB 10.11; 6S
My recommendation on a data only drive is a minimum 1% free also. I start looking for a new drive when I hit 3-5% free. That could be a little high with the size of today's drives I just don't know. Not even sure what would happen filling up a data drive down to .05 or .01% with the sizes of todays drives.

But, I'm afraid. Don't think I've tried taking even a data only drive down below 1% since the early 90s.

The issue is that when you're dealing with large files, that last 1% can disappear before you know it.
 
Last edited:

Slydude

Well-known member
Staff member
Moderator
Joined
Nov 15, 2009
Messages
17,595
Reaction score
1,071
Points
113
Location
North Louisiana, USA
Your Mac's Specs
M1 MacMini 16 GB - Ventura, iPhone 14 Pro Max, 2015 iMac 16 GB Monterey
I had a drive in a NAS a while back and made a mistake copying files. Given the number and size of the files it's highly likely this pushed free space at or below 1%. I say highly likely because the copy operation did not finish and also didn't throw up a warning. I finally had to cut power. The end result is that the drive directory structure was completely borked.
 

Shop Amazon


Shop for your Apple, Mac, iPhone and other computer products on Amazon.
We are a participant in the Amazon Services LLC Associates Program, an affiliate program designed to provide a means for us to earn fees by linking to Amazon and affiliated sites.
Top