I created a snapshot of an instance on OpenStack using the web interface Horizon. I see that the image size is 59.5 GB:

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I am surprised because the instance's disk was pretty empty:

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and the RAM mostly unused:

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How comes the image size is so large in comparison with the disk/RAM usage? (59.5 GB)

This instance size was was pretty big: 16core | 64GB RAM | 16 VCPU | 64.0GB Disk. Is the the image size impacted by the instance size, and if so why?


Try running the virt-sparsify tool from libguestfs on a copy of the image. If (as I suspect) it makes the image radically smaller, that would confirm your theory, that the total size of the instance disk is impacting the image size, rather than the amount of space actually used for files.

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