Re: [Engine-devel] SharedRawDisk feature detail

[Itamar Heim]

On 02/14/2012 07:44 PM, Livnat Peer wrote:
On 14/02/12 11:44, Maor wrote:
On 02/14/2012 09:17 AM, Livnat Peer wrote:
On 13/02/12 19:44, Maor wrote:
On 02/12/2012 07:03 PM, Livnat Peer wrote:
On 02/02/12 17:15, Maor wrote:
Hello all,
The shared raw disk feature description can be found under the following
links:
   http://www.ovirt.org/wiki/Features/DetailedSharedRawDisk
   http://www.ovirt.org/wiki/Features/SharedRawDisk

Please feel free, to share your comments.

Regards,
Maor
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Hi Maor,

- "when taking a VM snapshot, a snapshot of the shared disk will not be
taken."
I think it is worth mentioning that the shared disk will be part of the
VM snapshot configuration. The disk will appear as unplugged.
Agreed, I changed it to the following:
when taking a vm snapshot, a snapshot of the shared disk should not be
taken, although it will be part of the VM snapshot configuration and the
disk will appear as unplugged.

- Move VM is deprecated in 3.1.
Right, I removed this anecdote from the wiki.

- It seems from the wiki that shared disk is not supported for template
but is supported for VM pool.
I am not sure how can we do that? iirc we create pool from template.
What I was thinking about, is that the administrator can take a VM from
the pool and attach it a shared disk, after the VM was created (for
testing).

The motivation for adding shared disk was that each entity that can be
added with a disk can also be added with shared disk.
Today, Administrator can add a disk to a VM from pool, which might be
wrong behaviour, so maybe its better not to support it...

What is the complexity of supporting shared disk in Templates? off the
top of my head it seems like it is more complicated to block shared
disks in templates than to support it. What do you think?
Implementation wize it might be less complex, the problem is the use
cases it raises,
some of them which I'm thinking about are:
* If the disk will be deleted from the DC, should we remove it from the
template? or leave an indication in the template that there was a shared
disk there, maybe should not allow to delete the disk in the first
place, until it is unattached from the template?

Since template configuration is 'read-only' you can not change a disk to
be plugged or unplugged.
I would say you can not delete a disk that is part of a template
regardless if it is shared or not.
So in that case template with shared disk, will block the user from
removing the shared disk from the DC.
Won't it will make the flow for the user a bit complicated.
User who wants to remove the shared disk, will need to remove the VM's
which are based on the template and then remove the template it self.

I see the complication of delete, we have similar complications for
delete regardless of shared disk (deleting disk with snapshots).

Other than delete can you think of other complicated scenarios?

if it makes things more complex, why not postpone this part of the 
feature to a later phase?
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