[openstack-dev] [nova] Distributed Database

Monty Taylor mordred at inaugust.com
Fri Apr 22 21:49:17 UTC 2016


On 04/22/2016 04:32 PM, Andrew Laski wrote:
>
>
> On Fri, Apr 22, 2016, at 04:27 PM, Ed Leafe wrote:
>> OK, so I know that Friday afternoons are usually the worst times to
>> write a blog post and start an email discussion, and that the Friday
>> immediately before a Summit is the absolute worst, but I did it anyway.
>>
>> http://blog.leafe.com/index.php/2016/04/22/distributed_data_nova/
>>
>> Summary: we are creating way too much complexity by trying to make Nova
>> handle things that are best handled by a distributed database. The
>> recent split of the Nova DB into an API database and separate cell
>> databases is the glaring example of going down the wrong road.
>>
>> Anyway, read it on your flight (or, in my case, drive) to Austin, and
>> feel free to pull me aside to explain just how wrong I am. ;-)
>
> I agree with a lot of what Monty wrote in his response. And agree that
> given a greenfield there are much better approaches that could be taken
> rather than partitioning the database.
>
> However I do want to point out that cells v2 is not just about dealing
> with scale in the database. The message queue is another consideration,
> and as far as I know there is not an analog to the "distributed
> database" option available for the persistence layer.
>
> Additionally with v1 we found that deployers have enjoyed being able to
> group their hardware with cells. Baremetal goes in this cell, SSD filled
> computes over here, and spinning disks over there. And beyond that
> there's the ability to create a cell, fill it with hardware, and then
> test it without plugging it up to the production API. Cells provides an
> entry point for poking at things that isn't available without it.
>
> I don't want to get too sidetracked on talking about cells. I just
> wanted to point out that cells v2 did not come to fruition due to a fear
> of distributed databases.

Totally! Sorry for being less clear in my ramblings. :)

>>
>>
>> --
>>
>> -- Ed Leafe
>>
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