cfdisk / parted larger disks than provisioned

[fwragge]

Hi,

I've generated and deployed an OVA via ovftool (running CentOS 6.2 on a ESXi 5.1). 

The VMs used to generate the OVA and to deploy it were both provisioned as 32GB. 

However, Linux ('cfdisk', 'parted /dev/sda unit GB print free' etc.) indicates that the disk size is 34GB.

Trying a 64GB VM, such tools report 68GB.

Is it normal to expect a ~ 2GB larger disk per 32GB of provisioned size?  If so, why?

Thanks.

[dabson · Accepted solution]

Many tools, such as "cfdisk", use the International System of Units (SI) prefixes in order to be consistent with how hard drive manufacturers convey size. For example a kilobyte is considered to equal 1,000 bytes.

vSphere/vCenter uses binary prefixes to indicate size. For example a kilobyte is considered to equal 1,024 bytes.

Why do the tools show 34 GB and vSphere 32 GB?

vSphere: 32 GiB = 32,768 MiB = 33,554,432 KiB = 34,359,738,368 B (note the lower case "i" conveys binary units)

cfdisk: 34,359,738,368 B = 34,359,739 kB = 34,360 MB = 34 GB

So yes, what you are seeing is expected. Nothing's wrong. Doesn't make things any less confusing though.