Hibari FAQ Page

Table of Contents

2. Hibari and Hadoop/HDFS

Hibari is a production-ready, distributed, key-value, big data store. Hibari uses chain replication for strong consistency, high-availability, and durability. Hibari has excellent performance especially for read and large value operations.

This FAQ may help answer some of your questions.



Where can I download the Hibari binary code package?

Sorry, Hibari binary packages are not available right now.


How can I download the Hibari source code repositories using Git?

Please see here for pointers to download the Hibari source code repositories using Git and Google’s repo helper tool.

2. Hibari and Hadoop/HDFS


Chain Replication is one of Hibari’s characteristics…

  • Question: Chain Replication is one of Hibari’s characteristics. HDFS of Hadoop has similar characteristics. I’m not able to understand the difference. Please describe specific differences?
  • Answer: Sorry, we are not familiar with the implementation of HDFS. We need to schedule time to research and to understand the implementation of HDFS. Thank you in advance for your patience.


Hibari’s Admin Server plays a role like Name Node of Hadoop…

  • Question: We understand Hibari’s Admin Server plays a role like Name Node of Hadoop and controls chains under a master and slave configuration. If the Hibari Admin server abnormally stops, a standby needs to replace it and continue operations. To what extent is Hibari’s Admin Server and standbys are synced? Is it a level of full sync to enable a shift to a standby without any data loss? Also, how long would a shift to a standby take (out-of-service time)?
  • Answer: Yes, a standby for Hibari’s Admin Server can resume full service without any data loss. All of Hibari’s Admin Server’s private state is stored in bootstrap bricks on disk. The storage of the boostrap bricks is managed by quorom replication. When the Admin Server is stopped (e.g. node shutdown) or crashes (e.g. power failure), a standy Admin server will take over, assume the master role, and restore the cluster’s state from the bootstrap bricks. In theory, the 20-30 seconds that are required for the Admin Server to restart could mean 20-30 seconds of negative service impact to Hibari clients. In practice, however, Hibari clients almost never notice when an Admin Server instance crashes and restarts. Everytime any change happens in Hibari clients (data nodes), then master Admin Server will update the information into memory and also both bootstrap bricks of master and standby Admin Server at the same time. Sync between Master and Standby will be done everytime there is any change in Hibari clients side.


Hibari’s Admin Server stores what state…

  • Question: In case of Name Node of Hadoop, since all inode information is stored in its memory, a huge memory needs to be implemented in alignment with the number of blocks within a whole cluster. Does Hibari similarly have tough memory requirements? Or, does Hibari store chain control information (equivalent to inode information), not in a memory, but in disks?
  • Answer: No, Hibari’s Admin Server does not have any tough memory requirements. Hibari’s Admin Server only keeps the following private state in memory (and on disk):

    • All table definitions and their configuration, e.g. consistent hashing parameters.
    • Status of all bricks and all chains.
    • Operational history of all bricks and all chains.


What about data locality…

  • Question: Hibari provides API’s that can be used like Hbase and Big Table. You also said linkage with Map Reduce is theoretically possible but not yet implemented. What we do not understand is data locality. Map reduce focuses on data locality and improves processing efficiency by processing on a node the data that the node has. Suppose that you need to develop a map-reduce framework for Hibari, is it possible to design that data locality is recognized? I.e., Does / can Hibari provide API or others to retrieve data from chains on a certain node or to retreive data from a group of nodes that constitute certain chains?
  • Answer: Yes. Hibari has APIs to retrieve data (keys or keys+values) across all chains and to retrieve data from single or multiple single chains. Using Hibari’s consistent hashing algorithm implementation, the application can control how keys are mapped to chains by a key hashing prefix and can control the relative chain storage by a chain weighting factor.


Hibari’s Thrift API…

  • Question: Hibari also supports Thrift API. How much gap in execution speed is there when using Erlang API and Thrift API?
  • Answer: So far, there has been no measurable performance gain or loss found between Hibari’s native Erlang, UBF/EBF, and Thrift API implementations.


Tools for multiple clusters…

  • Question: Does Hibari provide tools to maintain many clusters?
  • Answer: No, not currently.


Maximum number of clusters…

  • Question: What is the maximum number of structured clusters that are theoretically possible? What is the max number of clusters that are actually proven?
  • Answer: Each Hibari cluster is an independent entity. There is no limit since there is no sharing between Hibari clusters.


Maximum number of nodes …

  • Question: What is the maximum number of nodes within a Hibari cluster that are theoretically possible? What is the max number of nodes that are actually proven?
  • Answer: There is no known theoretical limit. The maximum size of a Hibari cluster has not yet been determined. A practical limit of approximately 200-250 nodes is likely. This limit is currently governed by the implementation of Hibari’s Admin Server and by the implementation of Erlang’s distribution. The largest proven deployment of Hibari is 50-60 nodes.