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These two parameters (defaulting to 512k) control the amount of erlang file buffer space to allocate for delayed_write and read_ahead when merging. This config parameter is *per merge task* of which there can be many for each open HanoiDB; and again multiplied by number of active vnodes in Riak. As such, this can config parameter is significant for the memory usage of a Riak with Hanoi, but setting it too low will kill the performance.
2.3 KiB
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
]},
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.
git clone git://github.com/basho/riak.gitcd riak/depsgit clone git://github.com/basho/hanoi.gitcd .../deps/hanoi/enable-hanoi