[openstack-dev] [nova] nova backup not working in stable/icehouse?

Preston L. Bannister preston at bannister.us
Sat Aug 30 20:04:40 UTC 2014

You are thinking of written-for-cloud applications. For those the state
should not persist with the instance.

There are a very large number of existing applications, not written to the
cloud model, but which could be deployed in a cloud. Those applications are
not all going to get re-written (as the cost is often greater than the
benefit). Those applications need some ready and efficient means of backup.

The benefits of the cloud-application model and the cloud-deployment model
are distinct.

The existing nova backup (if it worked) is an inefficient snapshot. Not
really useful at scale.

There are two basic paths forward, here.  1) Build a complete common backup
implementation that everyone can use. Or 2) define a common API for
invoking backup, allow vendors to supply differing implementations, and add
to OpenStack the APIs needed by backup implementations.

Given past history, there does not seem to be enough focus or resources to
get (1) done.

That makes (2) much more likely. Reasonably sure we can find the interest
and resources for this path. :)

On Fri, Aug 29, 2014 at 10:55 PM, laserjetyang <laserjetyang at gmail.com>

> I think the purpose of nova VM is not for persistent usage, and it should
> be used for stateless. However, there are use cases to use VM to replace
> bare metal applications, and it requires the same coverage, which I think
> VMware did pretty well.
> The nova backup is snapshot indeed, so it should be re-implemented to be
> fitting into the real backup solution.
> On Sat, Aug 30, 2014 at 1:14 PM, Preston L. Bannister <
> preston at bannister.us> wrote:
>> The current "backup" APIs in OpenStack do not really make sense (and
>> apparently do not work ... which perhaps says something about usage and
>> usability). So in that sense, they could be removed.
>> Wrote out a bit as to what is needed:
>> http://bannister.us/weblog/2014/08/21/cloud-application-backup-and-openstack/
>> At the same time, to do efficient backup at cloud scale, OpenStack is
>> missing a few primitives needed for backup. We need to be able to quiesce
>> instances, and collect changed-block lists, across hypervisors and
>> filesystems. There is some relevant work in this area - for example:
>> https://wiki.openstack.org/wiki/Nova/InstanceLevelSnapshots
>> Switching hats - as a cloud developer, on AWS there is excellent current
>> means of backup-through-snapshots, which is very quick and is charged based
>> on changed-blocks. (The performance and cost both reflect use of
>> changed-block tracking underneath.)
>> If OpenStack completely lacks any equivalent API, then the platform is
>> less competitive.
>> Are you thinking about backup as performed by the cloud infrastructure
>> folk, or as a service used by cloud developers in deployed applications?
>> The first might do behind-the-scenes backups. The second needs an API.
>> On Fri, Aug 29, 2014 at 11:16 AM, Jay Pipes <jaypipes at gmail.com> wrote:
>>> On 08/29/2014 02:48 AM, Preston L. Bannister wrote:
>>>> Looking to put a proper implementation of instance backup into
>>>> OpenStack. Started by writing a simple set of baseline tests and running
>>>> against the stable/icehouse branch. They failed!
>>>> https://github.com/dreadedhill-work/openstack-backup-scripts
>>>> Scripts and configuration are in the above. Simple tests.
>>>> At first I assumed there was a configuration error in my Devstack ...
>>>> but at this point I believe the errors are in fact in OpenStack. (Also I
>>>> have rather more colorful things to say about what is and is not
>>>> logged.)
>>>> Try to backup bootable Cinder volumes attached to instances ... and all
>>>> fail. Try to backup instances booted from images, and all-but-one fail
>>>> (without logged errors, so far as I see).
>>>> Was concerned about preserving existing behaviour (as I am currently
>>>> hacking the Nova backup API), but ... if the existing is badly broken,
>>>> this may not be a concern. (Makes my job a bit simpler.)
>>>> If someone is using "nova backup" successfully (more than one backup at
>>>> a time), I *would* rather like to know!
>>>> Anyone with different experience?
>>> IMO, the create_backup API extension should be removed from the Compute
>>> API. It's completely unnecessary and backups should be the purview of
>>> external (to Nova) scripts or configuration management modules. This API
>>> extension is essentially trying to be a Cloud Cron, which is inappropriate
>>> for the Compute API, IMO.
>>> -jay
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