[Engine-devel] 'deactivate' disk - what's the use case?

[Simon Grinberg]

----- Original Message -----
> From: "Yaniv Kaul" <ykaul at redhat.com>
> To: "Livnat Peer" <lpeer at redhat.com>
> Cc: engine-devel at ovirt.org
> Sent: Tuesday, June 12, 2012 2:14:00 PM
> Subject: Re: [Engine-devel] 'deactivate' disk - what's the use case?
> 
> On 06/12/2012 12:47 PM, Livnat Peer wrote:
> > On 12/06/12 12:40, Yaniv Kaul wrote:
> >> On 06/12/2012 12:34 PM, Itamar Heim wrote:
> >>> On 06/12/2012 12:25 PM, Yaniv Kaul wrote:
> >>>> I'm wondering what's the usefulness of having dual action of
> >>>> attach +
> >>>> activate to get a disk properly attached and working in a VM
> >>>> (and the
> >>>> deactivate and detach counterparts).
> >>>>
> >>>> The only reason I can think of is that we've annoyed the user by
> >>>> this
> >>>> useless dual action when working with storage domains in a data
> >>>> center
> >>>> for ages, and we wish to remain consistent and annoy the user in
> >>>> the
> >>>> disks scenario as well, but there may be a reason I'm not aware
> >>>> of.
> >>> deactivated is like having a disk in offline, or hot unplugging
> >>> when
> >>> you still want to retain it in the context of the vm
> >>> configuration
> >> I understand that, I just argue it's quite useless (offline can be
> >> done
> >> from within the guest OS),
> > You can deactivate the disk if for some reason it blocks the guest
> > from
> > starting. I think that if the disk not accessible the VM won't
> > start and
> > then you can deactivate the disk and start the VM.
> 
> You can also detach it to get the same effect with one less click of
> a
> button or an API call.

And then if you did it manually for 20 VMs as a temporary measure, you'll have to re-attach it to the VMs. Will you remember to which VM you should attach each of your floating disks? You may have to now consult event log. 
(And in any case you'll need better search capabilities on disk then what you have now)

There are use cases to have an off-line disks, the issue is how not to annoy the user. 
I think I've suggested in the past that by default:
Attach = Attach + set_Online
Detach = set_offline + Detach. 
Unless explicitly stated otherwise by the user.

Thus you do not annoy the user but still maintain the functionality.


> Y.
> 
> >
> >
> >> does not work that way in physical hardware
> >> (offline is a logical action within the OS), has very little value
> >> to
> >> the RHEV Admin (unless he's paranoid and afraid that the disk will
> >> become float and someone else would 'steal' it from his VM) and is
> >> annoying to require multiple actions.
> >> Y.
> >>
> >>>> TIA,
> >>>> Y.
> >>>> _______________________________________________
> >>>> Engine-devel mailing list
> >>>> Engine-devel at ovirt.org
> >>>> http://lists.ovirt.org/mailman/listinfo/engine-devel
> >>
> >> _______________________________________________
> >> Engine-devel mailing list
> >> Engine-devel at ovirt.org
> >> http://lists.ovirt.org/mailman/listinfo/engine-devel
> 
> 
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