Thanks for the input, Gregory and Josh.

What I am hearing is that this has everything to do with the
filesystem, and nothing to do with the block device on Ceph.

Thanks again,

 - Travis

On Wed, Oct 10, 2012 at 1:55 PM, Gregory Farnum <g...@inktank.com> wrote:
> I don't know the ext4 internals at all, but filesystems tend to
> require allocation tables of various sorts (for managing extents,
> etc). 7.5GB out of 500GB seems a little large for that metadata, but
> isn't ridiculously so...
>
> On Wed, Oct 10, 2012 at 10:28 AM, Damien Churchill <dam...@gmail.com> wrote:
>> On 10 October 2012 18:10, Travis Rhoden <trho...@gmail.com> wrote:
>>> Additionally, 500G - 7.5G != 467G (the number shown as Avail).  Why
>>> the huge discrepancy?  I don't expect the numbers to add up exact due
>>> to rounding from kB, MB, GB, etc, but they should be darn close, a la
>>
>> ext4 keeps some reserved space, 5% by default, for when the disk is
>> full so you are still able to use the filesystem and clean it up.
>>
>> 500G * 0.05 = 25G
>> 500G - (25G + 7.5G) = 467G
>>
>> Can't tell you where the 7.5G comes from though!
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