[libvirt-users] Reintroduce "allocate entire disk" checkbox on virt-manager

[Gionatan Danti]

Il 20-06-2018 01:06 Gionatan Danti ha scritto:
> Il 19-06-2018 22:16 Cole Robinson ha scritto:
>> Sorry, I misunderstood. You can still achieve what you want but it's
>> more clicks: new vm, manage storage, add volume, and select raw volume
>> with whatever capacity you want but with 0 allocation.
> 
> Sure, but the automatic disk creation is very handy and much less error 
> prone.
> As it is now, if using a fallocate-less filesystem (eg: ZFS) and *not*
> selecting to create a custom disk, you risk waiting minutes or hours
> for libvirt to fully allocate the image by writing 0s to the disk
> file. This can wreck havok on SSDs and other eundurance-limited
> medium.
> 
>> qcow2 is the default for virt-manager because it enables features like
>> snapshots out of the box. The main motivation I have largely heard for
>> wanting raw over qcow2 is performance, but then using sparse raw
>> actually makes raw less performant, so it's kind of a weird middle
>> ground. For that reason I don't think it warrants adding back the
>> checkbox to the new VM UI since I think it's a fairly obscure use 
>> case,
>> and it can be achieved through the 'manage storage' wizard albeit with
>> more clicks
>> 
>> - Cole
> 
> On CoW filesystems, sparse RAW files are faster then Qcow2 ones.
> Moreover, avoiding double CoW is important for SSDs (which have
> limited lifespan). Even on XFS, sparse RAW files should be faster in
> the long run than Qcow2 files, due to no weird limitation on L2 chunk
> cache size.
> 
> I found the checkbox quite self-explanatory and very handy. Any
> chances to reconsider your decision?
> Thanks.

Hi, sorry for the bump... any feedback about that?
Thanks.

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Danti Gionatan
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