[Engine-devel] Empty cdrom drive.

[Livnat Peer]

On 15/02/12 11:29, Miki Kenneth wrote:
> 
> 
> ----- Original Message -----
>> From: "Ayal Baron" <abaron at redhat.com>
>> To: "Yaniv Kaul" <ykaul at redhat.com>
>> Cc: engine-devel at ovirt.org
>> Sent: Wednesday, February 15, 2012 11:23:54 AM
>> Subject: Re: [Engine-devel] Empty cdrom drive.
>>
>>
>>
>> ----- Original Message -----
>>> On 02/15/2012 09:44 AM, Igor Lvovsky wrote:
>>>>    Hi,
>>>> I want to discuss $subject on the email just to be sure that we
>>>> all
>>>> on the
>>>> same page.
>>>>
>>>> So, today in 3.0 vdsm has two ways to create VM with cdrom :
>>>>   1. If RHEV-M ask to create VM with cdrom, vdsm just create it
>>>>   2. RHEV-M doesn't ask to create VM with cdrom, vdsm still
>>>>   creates
>>>>   VM with
>>>>      empty cdrom. Vdsm creates this device as 'hdc' (IDE device,
>>>>      index 2),
>>>>      because of libvirt restrictions.
>>>>      In this case RHEV-M will be able to "insert" cdrom on the
>>>>      fly
>>>>      with
>>>>      changeCD request.
>>>>
>>>> In the new style API we want to get rid from stupid scenario #2,
>>>> because
>>>> we want to be able to create VM without cdrom at all.
>>>> It means, that now we need to change a little our scenarios:
>>>>   1. If RHEV-M ask to create VM with cdrom, vdsm just create it
>>>>   2. RHEV-M doesn't want to create VM with cdrom, but it want to
>>>>   be
>>>>   able to
>>>>      "insert" cdrom on the fly after this. Here we have two
>>>>      options:
>>>>      a. RHEV-M should to pass empty cdrom device on VM creation
>>>>      and
>>>>      use
>>>>         regular changeCD after that
>>>>      b. RHEV-M can create VM without cdrom and add cdrom later
>>>>      through
>>>>         hotplugDisk command.
>>>>


The preferred solution IMO would be to let the user choose if he wants a
VM with CD or not.
I think the motivation for the above is to 'save' IDE slot if a user
does not need CD.

If the user wants to have a VM with CD the engine would create an empty
CD and pass it to VDSM as a device, but if the user does not require a
CD there is no reason to create it in VDSM nor in the OE (oVirt Engine).

Supporting the above requires the engine upgrade to create empty CD
device to all VMs.

Dan - what happens in 3.0 API if the engine passes the element cdrom but
with empty path attribute. (I know that if the engine does not pass
cdrom element VDSM creates empty CD)


Livnat


>>>> Note: The new libvirt remove previous restriction on cdrom
>>>> devices.
>>>> Now
>>>>        cdrom can be created as IDE or VIRTIO device in any index.
>>>>        It means we can easily hotplug it.
>>>
>>> I didn't know a CDROM can be a virtio device, but in any way it
>>> requires
>>> driver (which may not exist on Windows).
>>> I didn't know an IDE CDROM can be hot-plugged (only USB-based?),
>>
>> It can't be hotplugged.
>> usb based is not ide (the ide device is the usb port, the cdrom is a
>> usb device afaik).
>>
>> The point of this email is that since we want to support being able
>> to start VMs *without* a cdrom then the default behaviour of
>> attaching a cdrom device needs to be implemented in engine or we
>> shall have a regression.
> This is a regression that we can not live with...
>> In the new API (for stable device addresses) vdsm doesn't
>> automatically attach a cdrom.
>>
>>> perhaps
>>> I'm wrong here.
>>> Y.
>>>
>>>>
>>>>
>>>> Regards,
>>>>      Igor Lvovsky
>>>>
>>>>
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