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Re: Question on Compression for Raw Image
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From: |
Kevin Wolf |
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Subject: |
Re: Question on Compression for Raw Image |
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Date: |
Tue, 20 Oct 2020 10:00:51 +0200 |
Am 20.10.2020 um 03:31 hat Wang, Wei W geschrieben:
> Hi,
>
> Does anyone know the reason why raw-format.c doesn't have compression
> support (but qcow has the supported added)? For example, raw image
> backup with compression, "qemu-img convert -c -O raw origin.img
> dist.img", doesn't work.
A raw image is by definition a file that contains the exact same
sequence of bytes as the guest sees, without any additional information
or encoding. If you compress a raw file, the guest will see compressed
data on its hard disk instead of the real data.
Anything you could do to add transparent compression to it would mean
that it's not a raw image any more, but a new image format.
Kevin