--- title: Getting started weight: -2 menu: main --- # Ozone - Object store for Apache Hadoop ## Introduction Ozone is a scalable distributed object store for Hadoop. Ozone supports RPC and REST APIs for working with Volumes, Buckets and Keys. Existing Hadoop applications can use Ozone transparently via a Hadoop Compatible FileSystem shim. ### Basic terminology 1. **Volumes** - Volumes are a notion similar to accounts. Volumes can be created or deleted only by administrators. 1. **Buckets** - A volume can contain zero or more buckets. 1. **Keys** - Keys are unique within a given bucket. ### Services in a minimal Ozone cluster 1. **Ozone Manager (OM)** - stores Ozone Metadata namely Volumes, Buckets and Key names. 1. **Storage Container Manager (SCM)** - handles Storage Container lifecycle. Containers are the unit of replication in Ozone and not exposed to users. 1. **DataNodes** - These are HDFS DataNodes which understand how to store Ozone Containers. Ozone has been designed to efficiently share storage space with HDFS blocks. ## Getting Started Ozone is currently work-in-progress and lives in the Hadoop source tree. The sub-projects (`hadoop-ozone` and `hadoop-hdds`) are part of the Hadoop source tree but they are not compiled by default and not part of official Apache Hadoop releases. To use Ozone, you have to build a package by yourself and deploy a cluster. ### Building Ozone To build Ozone, please checkout the Hadoop sources from the [Apache Hadoop git repo](https://git-wip-us.apache.org/repos/asf?p=hadoop.git). Then checkout the `trunk` branch and build it with the `hdds` profile enabled. ` git checkout trunk mvn clean package -DskipTests=true -Dmaven.javadoc.skip=true -Pdist -Phdds -Dtar -DskipShade ` `skipShade` is just to make compilation faster and not required. This builds a tarball in your distribution directory which can be used to deploy your Ozone cluster. The tarball path is `hadoop-dist/target/ozone-${project.version}.tar.gz`. At this point you can either setup a physical cluster or run Ozone via docker. ### Running Ozone via Docker This is the quickest way to bring up an Ozone cluster for development/testing or if you just want to get a feel for Ozone. It assumes that you have docker installed on the machine. Go to the directory where the docker compose files exist and tell `docker-compose` to start Ozone. This will start SCM, OM and a single datanode in the background. ``` cd hadoop-dist/target/compose/ozone docker-compose up -d ``` Now let us run some workload against Ozone. To do that we will run _freon_, the Ozone load generator after logging into one of the docker containers for OM, SCM or DataNode. Let's take DataNode for example:. ``` docker-compose exec datanode bash ozone freon -mode offline -validateWrites -numOfVolumes 1 -numOfBuckets 10 -numOfKeys 100 ``` You can checkout the OM UI to see the requests information. ``` http://localhost:9874/ ``` If you need more datanodes you can scale up: ``` docker-compose up --scale datanode=3 -d ``` ## Running Ozone using a real cluster ### Configuration First initialize Hadoop cluster configuration files like hadoop-env.sh, core-site.xml, hdfs-site.xml and any other configuration files that are needed for your cluster. #### Update hdfs-site.xml The container manager part of Ozone runs inside DataNodes as a pluggable module. To activate ozone you should define the service plugin implementation class. **Important**: It should be added to the **hdfs-site.xml** as the plugin should be activated as part of the normal HDFS Datanode bootstrap. ``` dfs.datanode.plugins org.apache.hadoop.ozone.HddsDatanodeService ``` #### Create ozone-site.xml Ozone relies on its own configuration file called `ozone-site.xml`. The following are the most important settings. 1. _*ozone.enabled*_ This is the most important setting for ozone. Currently, Ozone is an opt-in subsystem of HDFS. By default, Ozone is disabled. Setting this flag to `true` enables ozone in the HDFS cluster. Here is an example, ``` ozone.enabled True ``` 1. **ozone.metadata.dirs** Administrators can specify where the metadata must reside. Usually you pick your fastest disk (SSD if you have them on your nodes). OM, SCM and datanode will write the metadata to these disks. This is a required setting, if this is missing Ozone will fail to come up. Here is an example, ``` ozone.metadata.dirs /data/disk1/meta ``` 1. **ozone.scm.names** Ozone is build on top of container framework. Storage container manager(SCM) is a distributed block service which is used by ozone and other storage services. This property allows datanodes to discover where SCM is, so that datanodes can send heartbeat to SCM. SCM is designed to be highly available and datanodes assume there are multiple instances of SCM which form a highly available ring. The HA feature of SCM is a work in progress. So we configure ozone.scm.names to be a single machine. Here is an example, ``` ozone.scm.names scm.hadoop.apache.org ``` 1. **ozone.scm.datanode.id** Each datanode that speaks to SCM generates an ID just like HDFS. This is a mandatory setting. Please note: This path will be created by datanodes if it doesn't exist already. Here is an example, ``` ozone.scm.datanode.id /data/disk1/scm/meta/node/datanode.id ``` 1. **ozone.scm.block.client.address** Storage Container Manager(SCM) offers a set of services that can be used to build a distributed storage system. One of the services offered is the block services. OM and HDFS would use this service. This property describes where OM can discover SCM's block service endpoint. There is corresponding ports etc, but assuming that we are using default ports, the server address is the only required field. Here is an example, ``` ozone.scm.block.client.address scm.hadoop.apache.org ``` 1. **ozone.ksm.address** OM server address. This is used by OzoneClient and Ozone File System. ``` ozone.ksm.address ksm.hadoop.apache.org ``` #### Ozone Settings Summary | Setting | Value | Comment | |--------------------------------|------------------------------|------------------------------------------------------------------| | ozone.enabled | True | This enables SCM and containers in HDFS cluster. | | ozone.metadata.dirs | file path | The metadata will be stored here. | | ozone.scm.names | SCM server name | Hostname:port or or IP:port address of SCM. | | ozone.scm.block.client.address | SCM server name and port | Used by services like OM | | ozone.scm.client.address | SCM server name and port | Used by client side | | ozone.scm.datanode.address | SCM server name and port | Used by datanode to talk to SCM | | ozone.ksm.address | OM server name | Used by Ozone handler and Ozone file system. | #### Sample ozone-site.xml ``` ozone.enabled True ozone.metadata.dirs /data/disk1/ozone/meta ozone.scm.names 127.0.0.1 ozone.scm.client.address 127.0.0.1:9860 ozone.scm.block.client.address 127.0.0.1:9863 ozone.scm.datanode.address 127.0.0.1:9861 ozone.ksm.address 127.0.0.1:9874 ``` ### Starting Ozone Ozone is designed to run concurrently with HDFS. The simplest way to [start HDFS](../hadoop-common/ClusterSetup.html) is to run `start-dfs.sh` from the `$HADOOP/sbin/start-dfs.sh`. Once HDFS is running, please verify it is fully functional by running some commands like - *./hdfs dfs -mkdir /usr* - *./hdfs dfs -ls /* Once you are sure that HDFS is running, start Ozone. To start ozone, you need to start SCM and OM. The first time you bring up Ozone, SCM must be initialized. ``` ozone scm -init ``` Start SCM. ``` ozone --daemon start scm ``` Once SCM gets started, OM must be initialized. ``` ozone ksm -createObjectStore ``` Start OM. ``` ozone --daemon start ksm ``` If you would like to start HDFS and Ozone together, you can do that by running a single command. ``` $HADOOP/sbin/start-ozone.sh ``` This command will start HDFS and then start the ozone components. Once you have ozone running you can use these ozone [shell](./OzoneCommandShell.html) commands to start creating a volume, bucket and keys. ## Diagnosing issues Ozone tries not to pollute the existing HDFS streams of configuration and logging. So ozone logs are by default configured to be written to a file called `ozone.log`. This is controlled by the settings in `log4j.properties` file in the hadoop configuration directory. Here is the log4j properties that are added by ozone. ``` # # Add a logger for ozone that is separate from the Datanode. # #log4j.debug=true log4j.logger.org.apache.hadoop.ozone=DEBUG,OZONE,FILE # Do not log into datanode logs. Remove this line to have single log. log4j.additivity.org.apache.hadoop.ozone=false # For development purposes, log both to console and log file. log4j.appender.OZONE=org.apache.log4j.ConsoleAppender log4j.appender.OZONE.Threshold=info log4j.appender.OZONE.layout=org.apache.log4j.PatternLayout log4j.appender.OZONE.layout.ConversionPattern=%d{ISO8601} [%t] %-5p \ %X{component} %X{function} %X{resource} %X{user} %X{request} - %m%n # Real ozone logger that writes to ozone.log log4j.appender.FILE=org.apache.log4j.DailyRollingFileAppender log4j.appender.FILE.File=${hadoop.log.dir}/ozone.log log4j.appender.FILE.Threshold=debug log4j.appender.FILE.layout=org.apache.log4j.PatternLayout log4j.appender.FILE.layout.ConversionPattern=%d{ISO8601} [%t] %-5p \ (%F:%L) %X{function} %X{resource} %X{user} %X{request} - \ %m%n ``` If you would like to have a single datanode log instead of ozone stuff getting written to ozone.log, please remove this line or set this to true. ``` log4j.additivity.org.apache.hadoop.ozone=false ``` On the SCM/OM side, you will be able to see 1. `hadoop-hdfs-ksm-hostname.log` 1. `hadoop-hdfs-scm-hostname.log` ## Reporting Bugs Please file any issues you see under [Apache HDDS Project Jira](https://issues.apache.org/jira/projects/HDDS/issues/). ## References - [Object store in HDFS: HDFS-7240](https://issues.apache.org/jira/browse/HDFS-7240) - [Ozone File System: HDFS-13074](https://issues.apache.org/jira/browse/HDFS-13074) - [Building HDFS on top of new storage layer (HDDS): HDFS-10419](https://issues.apache.org/jira/browse/HDFS-10419)