Wednesday, April 13, 2011

Installing Greenplum SNE / CE

After understanding basics of Greenplum, let’s Setup Greenplum Community edition (CE) or single node edition (SNE). In this Greenplum tutorial we will see how to install and Initialize Greenplum Database SNE. This section provides instructions on how to install the Greenplum Database SNE software and get your single-node Greenplum Database SNE system up and running. In the following Greenplum quick start we will use CentOS 5.X or above.
Before installing we have to change following OS configuration parameters:
Set the following parameters in the /etc/sysctl.conf file and reboot:
kernel.shmmax = 500000000
kernel.shmmni = 4096
kernel.shmall = 4000000000
kernel.sem = 250 64000 100 512
net.ipv4.tcp_tw_recycle=1
net.ipv4.tcp_max_syn_backlog=4096
net.core.netdev_max_backlog=10000
vm.overcommit_memory=2
Set the following parameters in the /etc/security/limits.conf file:
* soft nofile 65536
* hard nofile 65536
* soft nproc 131072
* hard nproc 131072
Add the Greenplum database Admin account:
# useradd gpadmin
# passwd gpadmin
# New password: password
# Retype new password: password
You cannot run the Greenplum Database SNE server as root. While dealing with Greenplum use this newly created user account
Installing the Greenplum Database SNE / Community edition:
1. Download or copy the Greenplum Database SNE / CE from:
www.greenplum.com/
2. Unzip the installer file:
# unzip greenplum-db-4.0.0.0-build-#-SingleNodeEdition-PLATFORM.zip
3. Launch the installer using bash:
# /bin/bash greenplum-db-4.0.0.0-build-#-SingleNodeEdition-PLATFORM.bin
4. The installer prompts you to provide an installation path. Press ENTER to accept the default install path (/usr/local/greenplum-db-4.0.0.0), or enter new path
5. The installer installs the Greenplum Database SNE /CE software and creates a greenplum-db symbolic link one directory level above your version-specific Greenplum Database SNE
6. Change the ownership of your Greenplum Database SNE installation so that it is owned by the gpadmin
# chown -R gpadmin /usr/local/greenplum-db-4.0.0.0
# chgrp -R gpadmin /usr/local/greenplum-db-4.0.0.0
7. Preparing the Data Directory Locations
Every Greenplum Database SNE instance has a designated storage area on disk that is called the data directory location.
8. Create or choose a directory that will serve as your master data storage area
On this location user data is not stored, instead metadata (data about the data) is stored. Here global system catalog resides
# mkdir /gpmaster
# chown gpadmin /gpmaster
# chgrp gpadmin /gpmaster
9. Create or choose the directories that will serve as your segment storage areas:
This is the file system location where the database data is stored.
# mkdir /gpdata1
# chown gpadmin /gpdata1
# chgrp gpadmin /gpdata1
# mkdir /gpdata2
# chown gpadmin /gpdata2
# chgrp gpadmin /gpdata2
10. Configuring Greenplum Database SNE / CE Environment Variables:
$ vi .bashrc
Then add following entry
source /usr/local/greenplum-db/greenplum_path.sh
now source it
$ source ~/.bashrc
11. Now let’s initialize Greenplum database:
Greenplum provides a utility called gpinitsystem which initializes a Greenplum Database system. After the Greenplum Database SNE system is initialized and started, you can then create and manage databases by connecting to the Greenplum master database process.
12. Log in to the system as the gpadmin user:
# su - gpadmin
13. Copy the single_hostlist example file from your Greenplum Database SNE installation to the current directory:
$ cp $GPHOME/docs/cli_help/single_hostlist_example/single_hostlist
14. Copy the gp_init_singlenode example file from your Greenplum Database SNE installation to the current directory:
$ cp $GPHOME/docs/cli_help/gp_init_singlenode_example/gp_init_singlenode
15. Edit the gp_init_singlenode file and enter your configuration settings, you can remain them default. Some default parameters in this file are:
ARRAY_NAME="GPDB SNE"
MACHINE_LIST_FILE=./single_hostlist
SEG_PREFIX=gpsne
PORT_BASE=50000
declare -a DATA_DIRECTORY=(/gpdata1 /gpdata2)
MASTER_HOSTNAME=127.0.0.1
MASTER_DIRECTORY=/gpmaster
MASTER_PORT=5432
16. Run the gpssh-exkeys utility to exchange ssh keys for the local host:
$ gpssh-exkeys -h 127.0.0.1
17. initialize Greenplum Database SNE:
$ gpinitsystem -c gp_init_singlenode
18. After the Greenplum Database SNE system is initialized and started, you can connect to the Greenplum master database process using the psql client program:
$ createdb mydb
$ psql mydb
19. Now export master data directory:
$ vi .bashrc
Then add following entry
export MASTER_DATA_DIRECTORY=/gpmaster/gpsne-1
now source it
$ source ~/.bashrc
20. Now you can perform any database operations using psql program (DDL, DML)
Uninstall Greenplum:
To uninstall run the following commands:
$ gpdeletesystem -d /gpmaster/gpsne-1
$ rm -rf /usr/local/greenplum-db-4.0.0.0
$ rm /usr/local/greenplum-db
You can remove the environment variable and restore the default setting of OS parameters(Optional)

Tuesday, April 5, 2011

Understanding Greenplum

This blog will guide you to understand Greenplum that includes what is Greenplum, its architecture, different segments, and its basics in details. In this Greenplum tutorial we will try to understand the capability and the architecture provided by Greenplum
 
What is Greenplum: Greenplum Database is a massively parallel processing (MPP) database server based on PostgreSQL open-source technology. MPP (also known as a shared nothing architecture) refers to systems with two or more processors which cooperate to carry out an operation - each processor with its own memory, operating system and disks.
Source: Greenplum
 
Greenplum Database Architecture: Greenplum Database utilizes a shared-nothing MPP (massively parallel processing) architecture. In this architecture, data is automatically partitioned across multiple 'segment' servers, and each 'segment' owns and manages a distinct portion of the overall data. All communication is via a network interconnect -- there is no disk-level sharing or contention to be concerned with (i.e. it is a 'shared-nothing' architecture). The segment servers are able to process every query in a fully parallel manner, use all disk connections simultaneously, and efficiently flow data between segments as query plans dictates
Source: Greenplum
 
 
Is Greenplum free: Greenplum is not free to setup for production or to setup cluster. But it has launched a community edition which is free but with pre specified guidelines.
 
What is Community edition: The EMC Greenplum Community Edition (CE) provides a powerful and comprehensive analytic environment enabling users to turn increasingly large amounts of data into useful insight. Developers, data scientists and other data professionals can experiment with real-world data, perform advanced analytics and most importantly - rapidly reveal insights from big data sets with ease
 
Parallel Query Optimizer: "Greenplum Database's parallel query optimizer is responsible for converting SQL or MapReduce into a physical execution plan." It does this using a cost-based optimization algorithm in which it evaluates a vast number of potential plans and selects the one that it believes will lead to the most efficient query execution.
 
Parallel Dataflow Engine:  At the heart of the Greenplum Database is the Parallel Dataflow Engine. This is where the real work of processing and analyzing data is done. Greenplum’s Parallel Dataflow Engine is highly optimized at executing both SQL and MapReduce, and does so in a massively parallel manner
 Source: Greenplum
 
 
Greenplum Database support (hardware requirements): Greenplum Database supported for production use on SUSE Linux Enterprise Server 10.2 (64-bit),  Red Hat Enterprise Linux 5.x (64-bit), CentOS Linux 5.x (64-bit) and Sun Solaris 10U5+ (64-bit). Greenplum Database 3.3 is supported on server hardware from a range of vendors including HP, Dell, Sun and IBM. Greenplum Database is supported for non-production (development and evaluation) use on Mac OSX 10.5, Red Hat Enterprise Linux 5.2 or higher (32-bit) and CentOS Linux 5.2 or higher (32-bit).
 
Greenplum Master Segment: "The master is the entry point to the Greenplum Database system. It is the database process that accepts client connections and processes the SQL commands issued by the users of the system". The master is where the global system catalog resides (the set of system tables that contain metadata about the Greenplum Database system itself), however the master does not contain any user data. Data resides only on the segments. The master does the work of authenticating client connections, processing the incoming SQL commands, distributing the work load between the segments, coordinating the results returned by each of the segments, and presenting the final results to the client program
 
Greenplum Primary Segments: In Greenplum Database, the segments are where the data is stored and where the majority of query processing takes place. User-defined tables and their indexes are distributed across the available number of segments in the Greenplum Database system, each segment containing a distinct portion of the data. Segment instances are the database server processes that serve segments. Users do not interact directly with the segments in a Greenplum Database system, but do so through the master.
 
Mirror Segment:Mirror segments allow database queries to fail over to a backup segment if the primary segment becomes unavailable. Mirror / secondary segment always resides on a different host than its primary
 
Source: Greenplum