Disclaimer: I wrote OpenTSDB.
I would say that the biggest advantage of Graphite seems to be superior graphing capabilities. It offers more graph types and features. Deployment complexity is also probably a bit lower with Graphite, as it’s not a distributed system and thus has fewer moving parts.
OpenTSDB, on the other hand, is capable of storing a significantly larger amount of fine-grained data points. This comes at the cost of deploying HBase, which isn’t that big of a deal to be honest. If you want to get real-time data down to the second with >>10k new data points/s, then OpenTSDB will suit you well.
Some info about our current scale at StumbleUpon (these numbers generally double every 2-3 months):
- Over 1B new data points per day (=12k/s on average).
- Hundreds of billions of data points stored.
- Less than 2TB of disk space consumed (before 3x replication by HDFS).
- Read queries are generally capable of retrieving, munging and plotting over 500k data points per second.