[df07]

The only thing that really hurts are the SQL Server licenses. Everything else (MSDN licenses for devs, OS licenses, etc.) are small percentages on the cost of hiring a dev or building a server. SQL Server pricing is a beast -- they know you're locked in, and it's carefully priced just under the "what if we just hired several people to do nothing but move us off of SQL Server" price point.

With that said, we're getting amazing performance out of SQL Server without having to shard, etc: all of Stack Overflow runs off a single server, and most of the rest of Stack Exchange runs off a second server.

[buckbova]

"Stack Overflow runs off a single server" that is a cluster of how many physical servers with how many processors and how much ram?

  Three Dell R720xd database servers (two in New York City, one in Oregon, using SQL AlwaysOn Clustering) (Global "Sites" DB & Stack Overflow dedicated):

  - 2x Intel Xeon Processor E5-2680 @ 2.70 GHz
  - 384 GB RAM
  - 21 drives
  - Mirrored Pair for OS
  - 16+1 Intel 710 200GB SSD RAID10 for databases
  - SQL Server 2014 CTP2
  - 2x 10Gb network team

[kmontrose]

David means a single primary, there's a read-only replica for in DC failover and a read-only replica in our other DC for "New York is getting hit by another hurricane"-failover.

A few services hit the read replicas instead of the primary (our API, for example, moves what it can when it can), but the code for stackoverflow.com is almost entirely querying a single (quite beefy) box.

We can and do sometimes run without either replica in the AG, though we prefer not to except for scheduled maintenance.

[noselasd]

The hardware specs as of December 2013 are here: http://meta.stackoverflow.com/questions/10369/which-tools-an...