PV size is reported as 50GB but is physically 54GB

[Alan McKinnon]

On Friday 01 September 2006 20:46, Gabriel M Dragffy wrote:
> Hi,
>
> I have a partition /dev/hds3 that is set as a physical volume
> for my LVM, a disc partitioning program will report the
> partition as being 54G, however the LVM says it is 50G, why
> would this be so?

The physical partition is 54G large, but the logical volume on 
it (most definitely *not* the same thing) is 50G - the rest is 
LVM overhead. It needs to initialize the partiton to make a pv 
out of it, the extents need to be created and tracked, and 
something somewhere is recording which extents are assigned to 
which lvs. All this takes space

> I also have another discrepency in sizes reported by LVM, or
> for example using df. However I have saved that for another
> topic as I think it is unrelated to this particular question.

This entire industry can't seem to make up it's mind as to 
exactly what a mega byte is. It can be:

1000 * 1000 bytes
1000 * 1024 bytes
1024 * 1024 bytes

and we have MB, Mb, mB and mb abbreviations to confuse the 
issue...

There is a standard somewhere for this kind of thing, but few 
folk seem to follow it. If you want to know how big an fs is, 
ask it's tools to give you the answer in an exact number of 
bytes.

alan