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How does openstack qcow2 image differ from ISO

asked 2015-11-01 09:59:07 -0500

naggappan gravatar image


In a normal machine we use the iso and install the OS. During the installation time we will specify the HDD partition to be used .

But when this comes to cloud aws/openstack we just pick up the image from glance and choose the flavor the VM gets sniped up and there is no instillation time required here .

Please explain me the full process how this actually happens in-depth. (Or provide me few links to understand this concept)

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Read about kvm virtualization the types of filesystem it supports and how to create a qcow2 disk, the concept would become clear.

soumitrakarmakar gravatar imagesoumitrakarmakar ( 2015-11-01 23:06:18 -0500 )edit

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answered 2015-11-02 21:31:59 -0500

shashidhar gravatar image

An ISO image file is a snapshot of the data and layout of a CD or DVD, saved in ISO-9660 format. This is used burn (create) various OS images on CD/DVD so that later directly used as bootable image.

The QCOW image format is one of the disk image formats supported by the QEMU processor emulator. This image is represented in fixed size block devices in a file. In general QCOW2 supports COW (Copy On Write) and will have smaller file sizes. This also supports snapshoting and zlib compression.

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answered 2015-11-01 23:09:16 -0500

soumitrakarmakar gravatar image

In short ISO is an optical disk image file whereas qcow2 is the partition/filesystem where an OS is already installed and can be used as template for spinning instances of the same OS type.

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Asked: 2015-11-01 09:59:07 -0500

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Last updated: Nov 01 '15