Fast Snapshot by copy qcow2 instance image and upload it into glance

Registered by Muhammad Hafiz Nasir on 2013-03-25

The current snapshot to clone an instance is taking too much time especially when the image size is huge (base + instance disk). To clone an instance faster, we just need to copy qcow2 image (instance disk) and upload it into glance. To run that instance, the image will be copied from glance to the newly created instance folder.

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Hi Muhammad Hafiz Nasir, we have implemented what you say in Essex, and we discarded it now, because this change cost more time when run_instance from snapshot, the reason is that, when you use normal image to create an instance, the base will be cached, and when the second time you create by the same image, the image doesn't need to be downloaded again, but when you create an instance by snapshot which only contains the CoW part 'disk', it needs to be downloaded everytime, if the size of snapshot is large(such as 10G+), the cost time of download image is terrible, and it will not be cached to save the download time. ----wangpan

Thanks for the feedback! -- Hafiz

Based on the summary above, what if when we run a new instance based on the snapshot, a new qcow2 image will be created instead of download it every time. So running snapshot still improve the time taken and preserving the timing when launching new instance -- Hafiz

@wangpan: for "when you create an instance by snapshot which only contains the CoW part 'disk', it needs to be downloaded everytime", i am wondering if the "disk" file is also cached, this will be not a issue, right?Hi Muhammad Hafiz Nasir, we have implemented what you say in Essex, and we discarded it now, because this change cost more time when run_instance from snapshot, the reason is that, when you use normal image to create an instance, the base will be cached, and when the second time you create by the same image, the image doesn't need to be downloaded again, but when you create an instance by snapshot which only contains the CoW part 'disk', it needs to be downloaded everytime, if the size of snapshot is large(such as 10G+), the cost time of download image is terrible, and it will not be cached to save the download time. ----wangpan

Thanks for the feedback! -- Hafiz

Based on the summary above, what if when we run a new instance based on the snapshot, a new qcow2 image will be created instead of download it every time. So running snapshot still improve the time taken and preserving the timing when launching new instance -- Hafiz

@wangpan: for "when you create an instance by snapshot which only contains the CoW part 'disk', it needs to be downloaded everytime", i am wondering if the "disk" file is also cached, this will be not a issue, right?

If you are still working on this, please re-submit via nova-specs. If not, please mark as obsolete, and add a quick comment to describe why. --johnthetubaguy (20th April 2014)

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