[batasrki]

The 'safe' feature isn't on by default, yet. Also, the benchmarks 10gen publishes are based on default setup, so basically, Mongo writes to RAM, therefore it's fast.

I love Mongo and am using it in a few apps, but their marketing does blow, I admit.

Also, Eliot Horowitz came out and bashed on Riak's eventual consistency promise by basically misleading devs into thinking that writing to MongoDB will always result in 'full consistency'. Listen to the ChangeLog episode on Mongo to hear that.

[kchodorow]

10gen doesn't publish any benchmarks. See http://www.mongodb.org/display/DOCS/Benchmarks for the official position.

I transcribed the MongoDB vs. Riak part of the Changelog webcast (available at http://thechangelog.com/post/3742814720/episode-0-5-1-mongod...):

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Riak and all the dynamo-style databases are really distributed key/value stores and I think, you know, I've never used Riak in production, but I have no reason not to believe it's not a very good, highly scalable distributed key/value store.

The difference between something like Riak and Mongo is that Mongo tries to solve a more generic problem. A couple of key points: one is consistency. Mongo is fully consistent, and all dynamo implementations are eventually consistent and for a lot of developers and a lot of applications, eventual consistency just is not an option. So I think for the default data store for a web site, you need something that's fully consistent.

The other major difference is just data model and query-ability and being able to manipulate data. So for example with Mongo you can index on any fields you want, you can have compound indexes, you can sort, you know, all the same types of queries you do with a relational database work with Mongo. In addition, you can update individual fields, you can increment counters, you can do a lot of the same kinds of update operations you would do with a relational database. It maps much closer to a relational database than to a key/value store. Key/value stores are great if you've got billions of keys and you need to store them, they'll work very well, but if you need to replace a relational database with something that is pretty feature-comparable, they're not designed to do that.

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It starts at minute 17.

edited: formatting.

[batasrki]

>Mongo is fully consistent

Can you please explain this for a case where there are multiple replica sets, the database is sharded and nodes are across data centers? What's sacrificed? Something must be.