[one-users] Few issues / concern about detach/attach operation of VM disks

[Carlos Martín Sánchez]

Hi,

On Wed, Jan 15, 2014 at 4:41 PM, kiran ranjane <kiran.ranjane at gmail.com>
 wrote:

> Hello Carlos,
>
> Thanks for the explanation, But the disk was using an image. The above
> suggestion would be good for one or two vms, What if I deploy 10 or more
> vms using same image (non persistent) and using a single Template?
>
> -- Each having their own Data-disk and each having different data in it,
> do you think the above suggestion would work?
> -- If I use the above procedure then I think I have to make 10 different
> clones of the image and Also 10 different templates to deploy the VMs,
> Which in my opinion is not feasible.
>
> If I am right, When I use non-persistent image a clone is created to
> system DS while deploying the VM, if this is correct then after the vm is
> deployed for such image it should keep the clone disk as persistent in the
> vm. This would help in deploying number of VMs from a single template and
> the data for that particular VM will also be persistent.
>

I think this fits the scenario described in request #2048 [1]


> Well the VM disk should have 3 buttons
>
> -- attach/detach (able to attach or detach same disk to the VM)
> -- Snapshot (Take snapshot Deferred/Hot)
> -- Delete (Delete the disk permanently from VM)
>
> What do you think on this, any suggestions?
>
> Thanks and reagrds
> Kiran Ranjane
>

If you could "instantiate to persistent" as described in #2048, the disk
would use an Image and the current attach+detach operations would not
delete the disk. I think that ticket would solve your use case, or is there
anything else missing?

Regards

PS: Please reply also to the mailing list.
[1] http://dev.opennebula.org/issues/2048
--
Carlos Martín, MSc
Project Engineer
OpenNebula - Flexible Enterprise Cloud Made Simple
www.OpenNebula.org | cmartin at opennebula.org |
@OpenNebula<http://twitter.com/opennebula><cmartin at opennebula.org>


On Wed, Jan 15, 2014 at 4:41 PM, kiran ranjane <kiran.ranjane at gmail.com>wrote:

> Hello Carlos,
>
> Thanks for the explanation, But the disk was using an image. The above
> suggestion would be good for one or two vms, What if I deploy 10 or more
> vms using same image (non persistent) and using a single Template?
>
> -- Each having their own Data-disk and each having different data in it,
> do you think the above suggestion would work?
> -- If I use the above procedure then I think I have to make 10 different
> clones of the image and Also 10 different templates to deploy the VMs,
> Which in my opinion is not feasible.
>
> If I am right, When I use non-persistent image a clone is created to
> system DS while deploying the VM, if this is correct then after the vm is
> deployed for such image it should keep the clone disk as persistent in the
> vm. This would help in deploying number of VMs from a single template and
> the data for that particular VM will also be persistent.
>
> Well the VM disk should have 3 buttons
>
> -- attach/detach (able to attach or detach same disk to the VM)
> -- Snapshot (Take snapshot Deferred/Hot)
> -- Delete (Delete the disk permanently from VM)
>
> What do you think on this, any suggestions?
>
> Thanks and reagrds
> Kiran Ranjane
>
>
>
> On Wed, Jan 15, 2014 at 8:22 PM, Carlos Martín Sánchez <
> cmartin at opennebula.org> wrote:
>
>> Hi,
>>
>> On Wed, Jan 15, 2014 at 2:08 PM, kiran ranjane <kiran.ranjane at gmail.com>
>>  wrote:
>>
>> Hello,
>>>
>>> Scenario :
>>>
>>> -- I created a VM from a template which had 2 disk (OS, Datablock).
>>> -- The VM was deployed properly in Running State and after that I tried
>>> the detach operation on Datablock disk. The disk was detached correctly
>>> without any errors but I want to attach the same disk again to the VM and
>>> there is no such way to do it in ONE.
>>>
>>
>> If the disk was volatile, it is lost. But if the disk was using an image,
>> you can attach that same image again. So I'd say that the use case is
>> supported, you just have to make sure that disks that may be used later
>> need to be backed by Images.
>>
>> -- The disk that are listed below in Storage tab under VM should be there
>>> even after you detach the disk from the VM so that in case we need it back
>>> we can attach the same disk again.
>>>
>>
>> This can be useful in some cases, but I'm not sure it is desirable in all
>> situations. If the disk is using a persistent Image, I'd expect that image
>> to be released, and ready to be used for another VM, as soon as the disk is
>> detached.
>>
>> -- Also we should have the option to move/attach the data-disk of a
>>> particular VM to any other VM.
>>>
>>
>> It is possible, if the disk is backed by an Image. You can detach +
>> detach to the other VM.
>>
>>
>>> -- Now if I detach the disk the data that is stored in that particular
>>> disk is gone. Is there a way to get it back?
>>>
>>
>> If it was a volatile disk, it was deleted when it was detached.
>>
>>
>> Maybe the requirement to manage persistency with Images is not intuitive,
>> but it is the OpenNebula model. First you define the storage, and then you
>> use it in the VMs.
>>
>> The only thing missing to fully support your use case may be a similar
>> operation to detach, but less definitive. Maybe an "unmount" action could
>> detach the disk without touching the files. I don't how useful it would be,
>> since it can be done from the guest. What do you think of this?
>>
>> Best regards
>> --
>> Carlos Martín, MSc
>> Project Engineer
>> OpenNebula - Flexible Enterprise Cloud Made Simple
>> www.OpenNebula.org | cmartin at opennebula.org | @OpenNebula<http://twitter.com/opennebula><cmartin at opennebula.org>
>>
>>
>
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