[Engine-devel] Issues with VirtIO-SCSI

[Vitor de Lima]

Hi Daniel,

I was referring to multiple types of controllers. For now, I think it is enough to have only one optional VirtIO-SCSI controller per VM, and (on the ppc64) one obligatory SPAPR VSCSI controller. The main question is how to handle the addresses when the VirtIO-SCSI is disabled and there is only the SPAPR VSCSI controller, and how to handle if the user enables VirtIO-SCSI after the creation of the VM (I think the addresses for the existing disks must remain stable, so the controller index must be 1 for the VirtIO-SCSI and 0 for the SPAPR VSCSI in this case).

Do you have any tips on how to implement the disk/cdrom addressing in these cases?

Thanks,
Vitor


>-----Original Message-----
>From: Daniel Erez [mailto:derez at redhat.com]
>Sent: terça-feira, 24 de setembro de 2013 09:31
>To: Vitor de Lima
>Cc: engine-devel at ovirt.org
>Subject: Re: [Engine-devel] Issues with VirtIO-SCSI
>
>
>
>----- Original Message -----
>> From: "Vitor de Lima" <vitor.lima at eldorado.org.br>
>> To: "Daniel Erez" <derez at redhat.com>
>> Cc: engine-devel at ovirt.org
>> Sent: Tuesday, September 24, 2013 12:34:17 AM
>> Subject: RE: [Engine-devel] Issues with VirtIO-SCSI
>>
>> Hi Daniel,
>>
>> I asked this question because I have implemented a filter to show only
>> compatible disk interfaces (in change #17964). The main purpose of
>> this patch is to hide the IDE interface type when creating disks for
>> PPC64 VMs (since IDE is not supported on this architecture). If it was
>> decided that the VirtIO-SCSI interface type should be hidden from the
>> user in case it was disabled, I would have to modify that patch a little bit.
>
>For consistency, I'll filter the interface from the list when VirtIO-SCSI is
>disabled.
>So yeah, keep that in mind when modifying your patch.
>
>>
>> Another issue is that in change #18622 the support for a
>> PPC64-specific controller, the SPAPR VSCSI controller, was introduced.
>> But the code was created based on the assumption that the VirtIO-SCSI
>> controller was always present, and this isn't the case anymore. And
>> another patch that I will work on really soon will add support to
>> create disks that are connected to this interface.
>
>Can you filter the option out or add a warning when VirtIO-SCSI is disabled?
>
>>
>> So, I would like some feedback before changing these patches. Is a
>> validation on the backend enough to block the user from using an inexistent
>controller?
>> Should the frontend be changed as well? What would be a good approach
>> to handle multiple SCSI controllers in a VM (were the presence of one
>> of them is optional)?
>
>You should block it in the engine on canDo and filter the option / warn about it
>in the UI.
>Regarding multiple controllers, are you referring to multiple types of
>controllers or just multiple VirtIO-SCSI devices?
>
>>
>> Thanks,
>> Vitor
>>
>>
>>
>> >-----Original Message-----
>> >From: Daniel Erez [mailto:derez at redhat.com]
>> >Sent: segunda-feira, 23 de setembro de 2013 17:06
>> >To: Vitor de Lima
>> >Cc: engine-devel at ovirt.org
>> >Subject: Re: [Engine-devel] Issues with VirtIO-SCSI
>> >
>> >Hi Vitor,
>> >
>> >The new VirtIO-SCSI enabled checkbox is an indication whether to
>> >attach a VirtIO-SCSI controller when running the VM.
>> >It should be enabled automatically on cluster >= 3.3.
>> >
>> >When disabled, I think it's preferable not to add a new controller
>> >automatically when running the VM as it requires creating/attaching a
>> >new VmDevice - which we refrain of on VmInfoBuilder flows (and since
>> >it might be confusing to the user...).
>> >
>> >As an alternative, I've planned to add a warning in the dialog or
>> >create a canDo message to prevent running the VM at all.
>> >I'm not sure we should hide the option from disk interfaces list as
>> >it's already being filtered using VirtIoScsiEnabled
>> >ConfigurationValue (and using OsInfo soon...).
>> >
>> >Let me know what you think and thanks a lot for the input!
>> >
>> >Daniel
>> >
>> >----- Original Message -----
>> >> From: "Vitor de Lima" <vitor.lima at eldorado.org.br>
>> >> To: engine-devel at ovirt.org
>> >> Sent: Monday, September 23, 2013 10:42:39 PM
>> >> Subject: [Engine-devel] Issues with VirtIO-SCSI
>> >>
>> >> Hi everyone,
>> >>
>> >> I have found some issues with this patch:
>> >>
>> >> http://gerrit.ovirt.org/#/c/18638/
>> >>
>> >> It allows the user to disable the VirtIO-SCSI disk interface during
>> >> the VM creation. The problem is that the user still can add, attach
>> >> and hotplug disks with the VirtIO-SCSI interface type, but when the
>> >> user does so, libvirt automatically creates a LSI Logic SCSI
>> >> controller and connects the new disk to it.
>> >>
>> >> How can this problem be solved? Should the VirtIO-SCSI interface
>> >> type be hidden from the user in case it wasn't enabled, or should
>> >> the engine enable the VirtIO-SCSI controller, hotplug it, then
>> >> hotplug the disk into it transparently?
>> >>
>> >> Thanks,
>> >> Vitor de Lima
>> >>
>> >> _______________________________________________
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>> >> Engine-devel at ovirt.org
>> >> http://lists.ovirt.org/mailman/listinfo/engine-devel
>> >>
>>