org.apache.hadoop.hdfs.server.diskbalancer.package-info Maven / Gradle / Ivy
/**
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
/**
* Disk Balancer connects to a {@link org.apache.hadoop.hdfs.server.datanode
* .DataNode} and attempts to spread data across all volumes evenly.
*
* This is achieved by :
*
* 1) Calculating the average data that should be on a set of volumes grouped
* by the type. For example, how much data should be on each volume of SSDs on a
* machine.
*
* 2) Once we know the average data that is expected to be on a volume we
* move data from volumes with higher than average load to volumes with
* less than average load.
*
* 3) Disk Balancer operates against data nodes which are live and operational.
*
*/
package org.apache.hadoop.hdfs.server.diskbalancer;