Open Stack

Hi,

We finally have ready for review all specifications required to support
High Availability Active/Active configurations in Cinder's Volume nodes.

There is a Blueprint to track this effort [1] and the specs are as follow:

- General description of the issues and solutions [2]
- Removal of Races on API nodes [3]
- Job distribution to clusters [4]
- Cleanup process of crashed nodes [5]
- Data corruption prevention [6]
- Removing local file locks from the manager [7]
- Removing local file locks from drivers [8]

The only effort that is in progress is the removal of code races on the
API nodes that has a series of patches but still needs reviewing and
more races need to be removed from the code.

I think it would be very beneficial for everyone if these patches were
reviewed before the Summit Sessions related to this topic, as it is a
complicated matter with many moving pieces and a good knowledge of the
topic will be essential to have productive sessions in Tokyo.

While I believe this is a viable path to implement HA A/A in Cinder,
these specifications can also be useful to anyone looking for other
solutions as it gives a detailed description of the problem as well as a
good number of cases that any proper solution needs to be able to
handle.

Alternatives to any of the issues are more than welcome, preferably
simpler ones, but they need to be well thought and must:

a) Take into account all cases of the issue that are trying to fix.

b) Play well with the other individual solutions as to give a reliable
global solution.

Cheers,
Gorka.


[1]: https://blueprints.launchpad.net/cinder/+spec/cinder-volume-active-active-support
[2]: https://review.openstack.org/232599
[3]: https://review.openstack.org/207101
[4]: https://review.openstack.org/232595
[5]: https://review.openstack.org/236977
[6]: https://review.openstack.org/237076
[7]: https://review.openstack.org/237602
[8]: https://review.openstack.org/237604