Re: [Xen-devel] [PATCH] vhd-util create: add -C|nocow option

[Chunyan Liu <cyliu@xxxxxxxx>]

2013/11/22 Jim Fehlig <jfehlig@xxxxxxxx>

Ian Jackson wrote:
> Ian Campbell writes ("Re: [Xen-devel] [PATCH] vhd-util create: add -C|nocow option"):
>
>> On Thu, 2013-11-21 at 15:46 +0800, Chunyan Liu wrote:
>>
>>> Add '-C' (nocow) option to vhd-util create.
>>>
>>> Btrfs has terrible performance when hosting VM images, even more when the guest
>>> in those VM are also using btrfs as file system. One way to mitigate this bad
>>> performance is to turn off COW attributes on VM files (since having copy on
>>> write for this kind of data is not useful). According to 'chattr' manpage, NOCOW
>>> could be set to new or empty file only on btrfs, so add a option here so that
>>> users could have a chance to set NOCOW to a vhd image.
>>>
>> Is there not some btrfs (or generic) utility which could be used to do
>> this after image creation rather than trying to build it in to every
>> utility which creates an image file?
>>
>
> This may seem like a daft question, but why do we even have a vhd
> utility in our tree ? ÂIs there not some vhd tools package that this
> should be in ?
>

Newer qemu-img supports vhd and vhdx right? ÂIs there even a need for
this tool at all anymore?

'qemu-img create' doesn't support creating vhd/vhdx format images. Only open/probe supported.
Â

Regards,
Jim

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