Fdisk disk size issue on RHEL 4

[Nigel Wade]

Anne Moore wrote:
> Greetings All
> 
> I'm using FDISK to slice up my RHEL 4 servers. However, when I input, for
> instance, "+50000M" for a 50 GIG partition, it actually only shows 46 GIG's
> after the partition is complete. This is upsetting my customer who believe
> I'm not doing things correctly. 
> 
> How do I determine how to get exactly the storage amount specified while
> using fdisk?
> 
> Thank you for you expert assistance.
> 
> Anne
> 

Is that 46GB for the filesystem size, or the partition size?

At the very least you want to work in units of 1024 not 1000. So that
should be 50*1024M i.e. 51200M. To get nearer you should really
calculate the size in bytes and that gives you 50*1024*1024*1024, or
53687MB.

Also, when creating the filesystem don't forget that mkfs normally
reserves 5% for root by default, which you can alter with the -m flag.
There are still filesystem overheads which you cannot remove.

If your customers really don't understand this, ask them to format a
500GB disk on their home PC and then explain why Windows tells them it's
not 500GB. (I presume they are normally Windows users, given their
demonstrated ability in the clueless department).

-- 
Nigel Wade, System Administrator, Space Plasma Physics Group,
            University of Leicester, Leicester, LE1 7RH, UK
E-mail :    nmw at ion.le.ac.uk
Phone :     +44 (0)116 2523548, Fax : +44 (0)116 2523555