[libvirt-users] Make discard='unmap' the default?

[Daniel P. Berrangé]

On Fri, Jun 01, 2018 at 07:54:32AM -0500, Ian Pilcher wrote:
> On 06/01/2018 05:19 AM, Daniel P. Berrangé wrote:
> > On Thu, May 31, 2018 at 02:34:15PM -0500, Ian Pilcher wrote:
> > > Is it possible to make discard='unmap' the default for virtio-scsi
> > > disks?  (Related, is it possible to make virtio-scsi the default disk
> > > type, rather than virtio-blk?)
> > 
> > This is really a question for whatever management tool you're using
> > with libvirt, since it is essentially defining an opinionated usage policy.
> 
> I'm using virt-manager.  I was under the impression that it gets its
> "hypervisor default" device types from libvirt.

Yes, it inherits some defaults to libvirt and/or QEMU. If those are not
suitable for some reason, then virt-manager needs to override it. The
decision about whether to enable discard or not is a policy decision
that doesn't have a single perfect answer. So changing it in libvirt
might make it better for you, but worse for someone else. Libvirt does
not want to get into such debates, so leaves such decisions for the app
above to make, where there may well be more global context/knowledge
allowing a better choice.

Regards,
Daniel
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