hanoidb/README.md

Hanoi Ordered Key/Value Storage

Hanoi implements an ordered key/value storage engine, implemented using "doubling sizes" persistent ordered sets of key/value pairs, much like LevelDB.

Here's the bullet list:

• Insert, Delete and Read all have worst case log₂(N) latency.
• Incremental space reclaimation: The cost of evicting stale key/values is amortized into insertion
  • you don't need a separate eviction thread to keep memory use low
  • you don't need to schedule merges to happen at off-peak hours
• Operations-friendly "append-only" storage
  • allows you to backup live system
  • crash-recovery is very fast and the logic is straight forward
  • All data subject to CRC32 checksums
• Supports efficient range queries
  • Riak secondary indexing
  • Fast key and bucket listing
• Uses bloom filters to avoid unnecessary lookups on disk
• Efficient resource utilization
  • Doesn't store all keys in memory
  • Uses a modest number of file descriptors proportional to the number of levels
  • IO is generally balanced between random and sequential
  • Low CPU overhead
• ~2000 lines of pure Erlang code in src/*.erl

Hanoi is developed by Trifork, a Riak expert solutions provider. You're most welcome to contact us if you want help optimizing your Riak setup.

Configuration options

Put these values in your app.config in the hanoi section

 {hanoi, [
          {data_root, "./data/hanoi"},
          {compress, none | snappy | gzip},
          {sync_strategy, none | sync | {seconds, N}},
          {page_size, 8192},
          {write_buffer_size, 524288},  % 512kB
          {read_buffer_size, 524288},  % 512kB

          %%
          %% The merge strategy is one of `fast' or `predictable'.
          %% Both have same log2(N) worst case, but `fast' is
          %% sometimes faster; yielding latency fluctuations.
          %%
          {merge_strategy, fast | predictable}
         ]},

How to deploy Hanoi as a Riak/KV backend

This storage engine can function as an alternative backend for Basho's 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