Hanoi Key/Value Storage Engine

This Erlang-based storage engine implements a structure somewhat like LSM-trees (Log-Structured Merge Trees, see docs/10.1.1.44.2782.pdf). The notes below describe how this storage engine work; I have not done extensive studies as how it differs from other storage mechanisms, but a brief brows through available online resources on LSM-trees indicates that this storage engine is quite different in several respects.

The storage engine can function as an alternative backend for Basho's Riak/KV.

Here's the bullet list:

• Very fast writes and deletes,
• Reasonably fast reads (N records are stored in log₂(N) B-trees),
• Operations-friendly "append-only" storage (allows you to backup live system, and crash-recovery is very simple)
• The cost of evicting stale key/values is amortized into insertion, so you don't need to schedule merge to happen at off-peak hours.
• Supports range queries (and thus eventually Riak 2i.)
• Doesn't need a boat load of RAM
• All in 1000 lines of pure Erlang code

Once we're a bit more stable, we'll provide a Riak backend.

Deploying the hanoi for testing with Riak/KV

You can deploy hanoi into a Riak devrel cluster using the enable-hanoi script. Clone the riak repo, change your working directory to it, and then execute the enable-hanoi script. It adds hanoi as a dependency, runs make all devrel, and then modifies the configuration settings of the resulting dev nodes to use the hanoi storage backend.

1. git clone git://github.com/basho/riak.git
2. cd riak/deps
3. git clone git://github.com/basho/hanoi.git
4. cd ..
5. ./deps/hanoi/enable-hanoi # which does make all devrel