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Ryu, the new mac_address table is going to associate a mac_address with an
instance and a network. When the VIFs are created for the instance, they are
given the mac_address from the table and attached to the network from the
table. Does that help?

-trey

On Mon, Mar 28, 2011 at 10:54 AM, Ishimoto, Ryu <ryu at midokura.jp> wrote:

>
> Thanks, that cleared it up for me.
>
> Staying on the topic of multi-nics, I have been trying to understand the
> direction in which Nova is going in regards to networking, and reading up on
> the multi-nics blueprint, it certainly seems like it's going in the right
> direction, but I do have one question:
>
> What was the reasoning behind associating networks, and not NICs, to an
> instance?  I understand that each instance NIC would belong to a distinct
> network, but it just seems more intuitive to imagine that an instance has
> NICs, and these NICs are connected to networks(or even more intuitively,
> connected to virtual ports that belong to various networks - Assigning a
> port to a NIC is like allocating an IP address).
>
> One problem I see from my suggestion above is that there is no association
> between NICs and networks, which means there is no way to select a network
> to grab an IP address from for each NIC at the time of VM launch.  I might
> be missing something completely here, but why not just let the user manage
> all this through the management  API before the VM launch?  Let the user
> create NICs, Networks(and Ports with IP addresses), and map the NICs to
> ports.  Then pass this list of 'connected' NICs as a parameter to launch a
> VM.  This parameter is optional, and if omitted, it should be treated as
> launching a single NIC instance, with a new NIC created and associated with
> the instance on the fly.  This prevents it from breaking the way it works
> now.
>
> If the concept of NICs for instance makes sense to everyone, I would love
> to help out and look further into what work needs to be done to extend the
> current multi-nic model into this one.
>
> I hope this made sense.  I apologize for the length.
>
> Thanks,
> Ryu
>
>
> On Tue, Mar 29, 2011 at 12:47 AM, Trey Morris <trey.morris at rackspace.com>wrote:
>
>> I've written a migration to handle moving the data in the current
>> instances table mac_address column into the new mac_address table before the
>> column is removed.
>>
>> I agree with Jay, data should never be discarded when migrating forward. I
>> don't think there has been a case yet where data is migrated in nova. This
>> could be the first.
>>
>> -trey
>>
>> On Mon, Mar 28, 2011 at 8:17 AM, Jay Pipes <jaypipes at gmail.com> wrote:
>>
>>> On Mon, Mar 28, 2011 at 2:31 AM, Ishimoto, Ryu <ryu at midokura.jp> wrote:
>>> > Hi All,
>>> > I was looking at the multi-nic
>>> > blueprint(https://blueprints.launchpad.net/nova/+spec/nova-multi-nic),
>>> and
>>> > in particular:
>>> > 1) removing mac_address column from the instances table and creating a
>>> > mac_addresses table. This is for storing which instances own which mac
>>> > addresses as well as which network each mac is for.
>>> > What happens(or should happen) to the MAC addresses that are already
>>> > associated with instances?  Will they be migrated to the new
>>> mac_addresses
>>> > table?  Or will they be discarded completely?
>>>
>>> Data should never be discarded in situations like this where a column
>>> is moved to another table's schema (or to be records in another
>>> table).
>>>
>>> > I was curious to know how Nova usually handles data migration issues
>>> like
>>> > this.
>>>
>>> No idea whether/if Nova's data migrations have previously needed to
>>> preserve data in this way. Glance does, however, and you can use the
>>> following Python changescript to get an idea how to perform this exact
>>> type of change:
>>>
>>>
>>> http://bazaar.launchpad.net/~glance-core/glance/cactus-trunk/view/head:/glance/registry/db/migrate_repo/versions/003_add_disk_format.py
>>>
>>> Note that SQLite has issues if you try to add and drop columns in the
>>> same changescript and you also have an unrelated column that is
>>> indexed (see:
>>> http://code.google.com/p/sqlalchemy-migrate/issues/detail?id=117).
>>> If this is the case, you will need to write SQL-based changescripts
>>> specfically for SQLite. You can see examples of how this is
>>> accomplished in Glance for the same DB version here:
>>>
>>>
>>> http://bazaar.launchpad.net/~glance-core/glance/cactus-trunk/view/head:/glance/registry/db/migrate_repo/versions/003_sqlite_upgrade.sql
>>>
>>> http://bazaar.launchpad.net/~glance-core/glance/cactus-trunk/view/head:/glance/registry/db/migrate_repo/versions/003_sqlite_downgrade.sql
>>>
>>> Cheers,
>>> jay
>>>
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