Expands an existing Greenplum Database across new hosts in the system.
gpexpand [{-f|--hosts-file} <hosts_file>]
| {-i|--input} <input_file> [-B <batch_size>]
| [{-d | --duration} <hh:mm:ss> | {-e|--end} '<YYYY-MM-DD hh:mm:ss>']
[-a|-analyze]
[-n <parallel_processes>]
| {-r|--rollback}
| {-c|--clean}
[-v|--verbose] [-s|--silent]
[{-t|--tardir} <directory> ]
[-S|--simple-progress ]
gpexpand -? | -h | --help
gpexpand --version
gpadmin).gpadmin user accountgpstart options -R or -m cannot be specified to start Greenplum Database.Note: These utilities cannot be run while gpexpand is performing segment initialization.
gpbackupgpcheckcatgpconfiggppkggprestoreImportant: When expanding a Greenplum Database system, you must deactivate Greenplum interconnect proxies before adding new hosts and segment instances to the system, and you must update the gp_interconnect_proxy_addresses parameter with the newly-added segment instances before you re-enable interconnect proxies. For information about Greenplum interconnect proxies, see Configuring Proxies for the Greenplum Interconnect.
For information about preparing a system for expansion, see Expanding a Greenplum Systemin the Greenplum Database Administrator Guide.
The gpexpand utility performs system expansion in two phases: segment instance initialization and then table data redistribution.
In the initialization phase, gpexpand runs with an input file that specifies data directories, dbid values, and other characteristics of the new segment instances. You can create the input file manually, or by following the prompts in an interactive interview.
If you choose to create the input file using the interactive interview, you can optionally specify a file containing a list of expansion system hosts. If your platform or command shell limits the length of the list of hostnames that you can type when prompted in the interview, specifying the hosts with -f may be mandatory.
In addition to initializing the segment instances, the initialization phase performs these actions:
In the table data redistribution phase, gpexpand redistributes table data to rebalance the data across the old and new segment instances.
Note: Data redistribution should be performed during low-use hours. Redistribution can be divided into batches over an extended period.
To begin the redistribution phase, run gpexpand with either the -d (duration) or -e (end time) options, or with no options. If you specify an end time or duration, then the utility redistributes tables in the expansion schema until the specified end time or duration is reached. If you specify no options, then the utility redistribution phase continues until all tables in the expansion schema are reorganized. Each table is reorganized using ALTER TABLE commands to rebalance the tables across new segments, and to set tables to their original distribution policy. If gpexpand completes the reorganization of all tables, it displays a success message and ends.
Note: This utility uses secure shell (SSH) connections between systems to perform its tasks. In large Greenplum Database deployments, cloud deployments, or deployments with a large number of segments per host, this utility may exceed the host's maximum threshold for unauthenticated connections. Consider updating the SSH MaxStartups and MaxSessions configuration parameters to increase this threshold. For more information about SSH configuration options, refer to the SSH documentation for your Linux distribution.
ANALYZE to update the table statistics after expansion. The default is to not run
ANALYZE.
Batch size of remote commands to send to a given host before making a one-second pause. Default is 16. Valid values are 1-128.
The gpexpand utility issues a number of setup commands that may exceed the host's maximum threshold for unauthenticated connections as defined by MaxStartups in the SSH daemon configuration. The one-second pause allows authentications to be completed before gpexpand issues any more commands.
gpexpand fails with connection errors such as
'ssh_exchange_identification: Connection closed by remote host.'
Specifies the name of a file that contains a list of new hosts for system expansion. Each line of the file must contain a single host name.
This file can contain hostnames with or without network interfaces specified. The gpexpand utility handles either case, adding interface numbers to end of the hostname if the original nodes are configured with multiple network interfaces.
Note: The Greenplum Database segment host naming convention is sdwN where sdw is a prefix and N is an integer. For example, sdw1, sdw2 and so on. For hosts with multiple interfaces, the convention is to append a dash (-) and number to the host name. For example, sdw1-1 and sdw1-2 are the two interface names for host sdw1.
Specifies the name of the expansion configuration file, which contains one line for each segment to be added in the format of:
The number of tables to redistribute simultaneously. Valid values are 1 - 96.
-n, check the current value of the server configuration parameter
max_connections and make sure the maximum connection limit is not exceeded.
If specified, the gpexpand utility records only the minimum progress information in the Greenplum Database table gpexpand.expansion_progress. The utility does not record the relation size information and status information in the table gpexpand.status_detail.
gpexpand utility copies a temporary tar file. The file contains Greenplum Database files that are used to create segment instances. The default directory is the user home directory.
When expanding a Greenplum Database system, you can specify either a hostname or an IP address for the value.
/etc/hosts file to map a hostname to an IP address. The resolution of a hostname to an IP address should not be performed by an external service such as a public DNS server. You must stop the Greenplum system before you change the mapping of a hostname to a different IP address.When expanding a Greenplum system, gpexpand populates gp_segment_configuration catalog table with the new segment instance information. Greenplum Database uses the address value of the gp_segment_configuration catalog table when looking up host systems for Greenplum interconnect (internal) communication between the master and segment instances and between segment instances, and for other internal communication.
If host systems are configured with multiple NICs, you can expand a Greenplum Database system to use each NIC as a Greenplum host system. You must ensure that the host systems are configured with sufficient resources to support all the segment instances being added to the host. Also, if you enable segment mirroring, you must ensure that the expanded Greenplum system configuration supports failover if a host system fails. For information about Greenplum Database mirroring schemes, see GUID-best_practices-ha.html#topic_ngz_qf4_tt.
For example, this is a gpexpand configuration file for a simple Greenplum system. The segment host gp6s1 and gp6s2 are configured with two NICs, -s1 and -s2, where the Greenplum Database system uses each NIC as a host system.
gp6s1-s2|gp6s1-s2|40001|/data/data1/gpseg2|6|2|p
gp6s2-s1|gp6s2-s1|50000|/data/mirror1/gpseg2|9|2|m
gp6s2-s1|gp6s2-s1|40000|/data/data1/gpseg3|7|3|p
gp6s1-s2|gp6s1-s2|50001|/data/mirror1/gpseg3|8|3|m
Run gpexpand with an input file to initialize new segments and create the expansion schema in the postgres database:
$ gpexpand -i input_file
Run gpexpand for sixty hours maximum duration to redistribute tables to new segments:
$ gpexpand -d 60:00:00
