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The "Hbase/MultipleMasters" page has been changed by LarsFrancke. The comment on this change is: typos, small corrections. http://wiki.apache.org/hadoop/Hbase/MultipleMasters?action=diff&rev1=4&rev2=5 -------------------------------------------------- '''This document is still a draft''' - Since version 0.20.0 (not released at this moment) HBase supports multiple Masters to provide higher availability. It works in the same way that Bigtable does as explained in the 2006 paper. This page contains the information you need to set it up, maintain it, and to understand how it works under the hood. + Since version 0.20.0 HBase supports multiple Masters to provide higher availability. It works in the same way that Bigtable does as explained in the 2006 paper. This page contains the information you need to set it up, maintain it, and to understand how it works under the hood. == Single Master Setup == - The [[http://hadoop.apache.org/hbase/docs/current/api/overview-summary.html#overview_description|Getting Started]] documentation describes set up with a single Master. A cluster can run without a Master for a number of few minutes but your regions will be unable to split. If it does happen, you can go to any other machine with the correct installation/configuration and do {{{$ ${HBASE_HOME}/bin/hbase-daemon.sh start master}}}. This newly started Master will take over Master functions. + The [[http://hadoop.apache.org/hbase/docs/current/api/overview-summary.html#overview_description|Getting Started]] documentation describes set up with a single Master. A cluster can run without a Master for a few minutes but your regions will be unable to split. If it does happen, you can go to any other machine with the correct installation/configuration and do {{{$ ${HBASE_HOME}/bin/hbase-daemon.sh start master}}}. This newly started Master will take over Master functions. - Currently the Hadoop Distributed Filesystem is '''not''' highly available so if the Namenode resides on the same machine is your Master, the cluster is still wedged and you will have to shut down HBase with a high probability of losing data. + Currently the Hadoop Distributed Filesystem is '''not''' highly available so if the Namenode resides on the same machine as your Master, the cluster is still wedged and you will have to shut down HBase with a high probability of losing data. == Multiple Masters Setup == @@ -16, +16 @@ === Basic knowledge === - The multi-master feature introduced in 0.20 does not add cooperating Masters; there is still just one working Master while the other ''backups'' wait. For example, if you start 200 Masters only 1 will be active while the others wait for it to die. The switch usually takes zookeeper.session.timeout plus a couple of seconds to occur. See "How it works inside" below for more information. + The multi-master feature introduced in 0.20.0 does not add cooperating Masters; there is still just one working Master while the other ''backups'' wait. For example, if you start 200 Masters only 1 will be active while the others wait for it to die. The switch usually takes `zookeeper.session.timeout` plus a couple of seconds to occur. See "How it works inside" below for more information. === Designing your highly available setup ===
