Re:MongoDB Finds A Major Adopter In Craigslist
by EwanToo on Tuesday May 17, 2011 @04:21AM
(#2555717)
Pretty much all distributed databases trade off ACID for speed, it's a fundamental issue with database design.
If you've got 20 database servers, potentially on the other side of the planet from each other, if you were to be ACID compliant throughout the cluster, each write commit would be delayed up to 500ms or more.
If you're running a pair of servers in the same room, as is normally the case with a traditional "active-active" database cluster, a network delay of 1ms often isn't a significant impact.
See http://mongodb-is-web-scale.com/ for a humorous angle on the speed vs. ACID compliance tradeoff.
It's great to see bigger users using Mongo because that's where these tests really take place. For example, it seems Cassandra got tested this way at Facebook/Reddit/Digg etc. and didn't cut it.