By a “cloud” database, I mean one with the following properties:

• provided as part of a hosting package by large web companies like Amazon, Google, Rackspace, Microsoft and even smaller ones like Joyent and Heroku.
• designed so that they scale up automatically as traffic and content grows, rather than requiring new architectural and deployment decisions to be made as traffic grows. The hardware behind a cloud is finite, but consumers should only bump into limitations as they approach the limits of the cloud itself, rather than the limits of a particular box or cluster.

Debate...

SQL Angel: “Relational database theory is powerful, and SQL is VERY flexible.”

Cloud Devil: “Our query languages are simpler, and you just can use programming code to do anything tricky (like summation or joining).”

SQL Angel: “Relational databases have been proven to scale. Like at stock exchanges and stuff. You just need to understand the query language, the optimizer, indexing, the disk layout, RAID striping, master-slave replication, read/write splitting, snapshot backups and the physics of  how hard disks spin. Just learn that stuff and you’ll be able to scale beautifully. With SQL, you’ll be the next eBay.”

Cloud Devil: “Our database just scales. Avoid huge numbers of writes to a single row. That’s all you need to learn about scalability. Everything else will just work. With your data in the cloud, you’ll be the next Google.”

SQL Angel: “You lose a lot of ad hoc query capability if you don’t use a database as flexible as a relational database. What about the analytics???”

Cloud Devil: “Analytics? Doesn’t that sound like some kind of stupid idea that would come out of marketing? Or Finance? Do you really need that? Anyhow, Google uses MapReduce for analytics. Major cloud databases either have, or will have access to MapReduce soon.”

SQL Angel: “But SQL databases are used in finance. Like at Goldman Sachs. Those guys are bad-ass enough to lend money to the country of Greece!”

Cloud Devil: “Cloud databases are used at Google. Those guys are bad-ass enough to give the Chinese government the finger.”

SQL Angel: “And there are free relational databases. Like MySQL! Which is used by Facebook and YouTube.”

Cloud Devil: “MySQL sucks. Facebook and YouTube are migrating away from it and onto Cassandra, BigTable, etc.”

SQL Angel: “But there are other free relational databases!”

Cloud Devil: “Wow….this is getting complicated. Do you really want to choose a minority relational database that for some reason is less popular than MySQL?

SQL Angel: “Plus there are some amazing commercial RDBMS’.”

Cloud Devil: “Before you have a dollar of revenue, you’re supposed to shell out cash for a commercial database? When App Engine is FREE and SimpleDB is CHEAP?”

SQL Angel: “SQL is a multi-vendor standard! You can port your code from one SQL engine to another!”

Cloud Devil: “Did you ever actually try porting SQL code and a large volume of data from one server to another? What a headache. If you pick something that scales all the way up from the start, you won’t have to worry about porting. Anyhow, maybe standards will arise for cloud databases too. Trust us.”

SQL Angel: “None of this is new…we already discarded this stuff in the 1960s!”

Cloud Devil: “Do you really care about stuff that happened before you were born? Anyhow, go ask the SQL guy about ‘paxos’ which was invented in 1998, ‘MapReduce’, patented in 2004 and ‘CAP Theorem’ from 2000. Ask about transparent sharding and automatic replication.”

SQL Angel: “The cloud devil is oversimplifying things. Look: SQL databases are just what PROFESSIONALS use.”

Cloud Devil: “Do you want things simple…or complex? Do you want to be like Google or like a Health Insurance company?”

Reference: http://www.ayogo.com/techblog/2010/03/buzzword-bingo-nosql-cloud-databases-are-a-disruptive-technology/

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