Excerpts from Mike Bayer's message of 2016-04-28 22:16:54 -0500: > > On 04/28/2016 08:25 PM, Edward Leafe wrote: > > > Your own tests showed that a single RDBMS instance doesn’t even break a > > sweat > > under your test loads. I don’t see why we need to shard it in the first > > place, especially if in doing so we add another layer of complexity and > > another dependency in order to compensate for that choice. Cells are a > > useful > > concept, but this proposed implementation is adding way too much complexity > > and debt to make it worthwhile. > > now that is a question I have also. Horizontal sharding is usually for > the case where you need to store say, 10B rows, and you'd like to split > it up among different silos. Nothing that I've seen about Nova suggests > this is a system with any large data requirements, or even medium size > data (a few million rows in relational databases is nothing). I > didn't have the impression that this was the rationale behind Cells, it > seems like this is more of some kind of logical separation of some kind > that somehow suits some environments (but I don't know how). > Certainly, if you're proposing a single large namespace of data across a > partition of nonrelational databases, and then the data size itself is > not that large, as long as "a single namespace" is appropriate then > there's no reason to break out of more than one MySQL database. There's > not much reason to transparently shard unless you are concerned about > adding limitless storage capacity. The Cells sharding seems to be > intentionally explicit and non-transparent. >
There's a bit more to it than the number of rows. There's also a desire to limit failure domains. IMO, that is entirely unfounded, as I've run thousands of servers that depended on a single pair of MySQL servers using simple DRBD and pacemaker with a floating IP for failover. This is the main reason MySQL is a thing... it can handle 100,000 concurrent connections just fine, and the ecosystem around detecting and handling failure/maintenance is mature. The whole cells conversation, IMO, stems from the way we use RabbitMQ. We should just stop doing that. I know as I move forward with our scaling efforts, I'll be trying several RPC drivers and none of them will go through RabbitMQ. __________________________________________________________________________ OpenStack Development Mailing List (not for usage questions) Unsubscribe: openstack-dev-requ...@lists.openstack.org?subject:unsubscribe http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-dev