Re: About sparse images

[Smart Weblications GmbH <info@smart-weblications.de>]

Am 26.08.2012 20:11, schrieb Sébastien Han:
> Hi all!
> 
> I know that ceph images (rbd) are sparse. It's good but I have some
> interrogations about the ceph -s (-w) output. Let's say your create a
> 10G image, map it, format it and mount it. Finally you filled up the
> entire space available. You notice that the 'data' and 'used' space
> had grown. Now delete the content of your image but **not** this
> image, not now. You notice that nothing changed from the ceph output,
> it's not surprising because of the sparse capability. At this point of
> time  the output from the command ceph is neither right nor wrong. It
> only shows the space used by the sparse image, but it doesn't mean
> that you have 'real' data in it, just a simple object allocation. It's
> not so relevant, the only solution is to remove the image (obviously).
> My feeling is that we should be careful about the ceph's output, it's
> not a good indicator for 'real' data. Ok Ceph won't replace a
> monitoring system but I'll be happy to trust the ceph output at 100%
> :)
> 
> I would appreciate some reactions about that :)
> 


why not gather real image size with rbd info <imagename>, sum up used space,
then look at ceph -s to get total avail space?



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