Google Compute Engine: what is the difference between disk snapshot and disk image?

google-compute-engine snapshot diskimage
Emmanuel picture Emmanuel · Dec 4, 2014 · Viewed 21.6k times · Source

I've been using both for my startup and to me, the functionality is the same. Until now, the instances I've been creating are only for computation. I'm wondering how GCE disk images and snapshots are different in terms of technology, and in which situation it is better to use one over the other.

Answer

Nacho Coloma picture Nacho Coloma · Apr 14, 2015

A snapshot reflects the contents of a persistent disk in a concrete instant in time. An image is the same thing, but includes an operating system and boot loader and can be used to boot an instance.

Images and snapshots can be public or private. In the case of images, public can mean official public images provided by Google or not.

Snapshots are stored as diffs (a snapshot is stored relative to the previous one, though that is transparent to you) while images are not. They are also cheaper ($0.03 per GB/month vs $0.085 for images).

These days the two concepts are quite similar. It's now possible to start an instance using a snapshot instead of an image, which is an easy way of resizing your boot partition. Using snapshots may be simpler for most cases.

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