[TriLUG] Disk space calculations in Linux

[Brian Henning]

A few shots in the dark...

Filesystem overhead, perhaps?

Root reservation (by default, 5% for mke3fs)?

Difference, as my elder namesake pointed out, of 10^3 vs 2^10?  i.e.

... "80GB" hard drive == 80,000,000,000 bytes (80 x SI "giga")
... 20% of that is 16,000,000,000 bytes (16 x SI "giga")
... a "GB" in the computer's mind is 2^30, or 1,073,741,824 bytes (1 x
binary "giga")
... 16,000,000,000 / 1,073,741,824 ~ 14.90 GB 

So, if it's an "80GB" drive and your friend is taking 20% and getting
14.90 binary-giga-bytes, he IS getting EXACTLY 16 SI-giga-bytes.

Minus the aforementioned filesystem overhead.

~B



-----Original Message-----
From: trilug-bounces at trilug.org [mailto:trilug-bounces at trilug.org] On
Behalf Of Mike Shaw
Sent: Thursday, January 24, 2008 4:29 PM
To: trilug
Subject: [TriLUG] Disk space calculations in Linux

Does anyone have a link to point to that explains disk space
calculations in
Linux?  For example, I need to explain to someone why it is that if you
take
20% of an 80G drive you don't automatically get EXACTLY 16G.

I was hoping not to have to re-invent this wheel and find a good link
that
had examples that I could direct someone to.

Thanks,

Mike
---
"Google HR wants to hire the smartest people still dumb enough to be
working
for somebody else." - Steve
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