raw vs. QCOW2ΒΆGlance supports a variety of image formats; however raw
and QCOW2 are the most common. While QCOW2 does provide
some benefits (supports copy-on-write, snapshots, dynamic expansion)
over the raw format, it should be noted that when images
are copied into Cinder volumes, they are converted into the raw
format once stored on an ONTAP backend.
The conversion of images from the QCOW2 to raw format
requires the qemu-img package. This must be installed on all
OpenStack Controller hosts.
Use of the QCOW2 image format is recommended for ephemeral disks
due to its inherent benefits when taking instance snapshots.
Use of the raw image format are recommended for persistent
boot disks.
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