Duplicating a Subcluster

Subclusters have many settings you can tune to get them to work just the way you want. After you have tuned a subcluster, you may want additional subclusters that are configured the same way. For example, suppose you have a subcluster that you have tuned to perform analytics workloads. To improve query throughput, you can create several more subclusters configured exactly like it. Instead of creating the new subclusters and then manually configuring them from scratch, you can duplicate the existing subcluster (called the source subcluster) to a new subcluster (the target subcluster).

When you create a new subcluster based on another subcluster, Vertica copies most of the source subcluster's settings. See below for a list of the settings that Vertica copies. These settings are both on the node level and the subcluster level.

Requirements for the Target Subcluster

You must have a set of hosts in your database cluster that you will use as the target of the subcluster duplication. Vertica forms these hosts into a target subcluster that receives most of the settings of the source subcluster. The hosts for the target subcluster must meet the following requirements:

• They must be part of your database cluster but not part of your database. For example, you can use hosts you have dropped from a subcluster or whose subcluster you have removed. Vertica returns an error if you attempt to duplicate a subcluster onto one or more nodes that are currently participating in the database.

  If you want to duplicate the settings of a subcluster to another subcluster, remove the target subcluster (see Removing Subclusters). Then duplicate the source subcluster onto the hosts of the now-removed target subcluster.

• The number of nodes you supply for the target subcluster must equal the number of nodes in the source subcluster. When duplicating the subcluster, Vertica performs a 1:1 copy of some node-level settings from each node in the source subcluster to a corresponding node in the target.
• The RAM and disk allocation for the hosts in the target subcluster should be at least the same as the source nodes. Technically, your target nodes can have less RAM or disk space than the source nodes. However, you will usually see performance issues in the new subcluster because the settings of the original subcluster will not be tuned for the resources of the target subcluster.

You can duplicate a subcluster even if some of the nodes in the source subcluster or hosts in the target are down. If nodes in the target are down, they use the catalog Vertica copied from the source node when they recover.

Duplication of Subcluster-level Settings

The following table lists the subcluster-level settings that Vertica copies from the source subcluster to the target.

Vertica does not copy the following subcluster settings:

Duplication of Node-level Settings

When Vertica duplicates a subcluster, it maps each node in the source subcluster to a node in the destination subcluster. Then it copies relevant node-level settings from each individual source node to the corresponding target node.

For example, suppose you have a three-node subcluster consisting of nodes named node01, node02, and node03. The target subcluster has nodes named node04, node05, and node06. In this case, Vertica copies the settings from node01 to node04, from node02 to node05, and from node03 to node06.

The node-level settings that Vertica copies from the source nodes to the target nodes are:

ALTER NODE node01 SET CompressCatalogOnDisk = 0;

Vertica does not copy the following node-level settings:

Using admintools to Duplicate a Subcluster

To duplicate a subcluster, you use the same admintools db_add_subcluster tool that you use to create a new subcluster (see Creating Subclusters). In addition to the required options to create a subcluster (the list of hosts, name for the new subcluster, database name, and so on), you also pass the --like option with the name of the source subcluster you want to duplicate.

The following examples demonstrate duplicating a three-node subcluster named analytics_1. The first example examines some of the settings in the analytics_1 subcluster:

• An override of the global TM resource pool's memory size.
• Its own resource pool named analytics
• Its membership in a subcluster-based load balancing group named analytics

=> SELECT name, subcluster_name, memorysize FROM SUBCLUSTER_RESOURCE_POOL_OVERRIDES;
 name | subcluster_name | memorysize 
------+-----------------+------------
 tm   | analytics_1     | 0%
(1 row)

=> SELECT name, subcluster_name, memorysize, plannedconcurrency 
      FROM resource_pools WHERE subcluster_name IS NOT NULL;
      name      | subcluster_name | memorysize | plannedconcurrency 
----------------+-----------------+------------+--------------------
 analytics_pool | analytics_1     | 70%        | 8
(1 row)

=> SELECT * FROM LOAD_BALANCE_GROUPS;
   name    |   policy   |  filter   |    type    | object_name 
-----------+------------+-----------+------------+-------------
 analytics | ROUNDROBIN | 0.0.0.0/0 | Subcluster | analytics_1
(1 row)

The following example calls admintool's db_add_subcluster tool to duplicate the analytics_1 subcluster onto a set of three hosts to create a subcluster named analytics_2.

$ admintools -t db_add_subcluster -d verticadb \
             -s 10.11.12.13,10.11.12.14,10.11.12.15 \
	      -p mypassword --like=analytics_1 -c analytics_2
	  
Creating new subcluster 'analytics_2'
Adding new hosts to 'analytics_2'
Eon database detected, creating new depot locations for newly added nodes
Creating depot locations for 1 nodes
 Warning when creating depot location for node: v_verticadb_node0007 
 WARNING: Target node v_verticadb_node0007 is down, so depot size has been 
          estimated from depot location on initiator. As soon as the node comes 
		  up, its depot size might be altered depending on its disk size
Eon database detected, creating new depot locations for newly added nodes
Creating depot locations for 1 nodes
 Warning when creating depot location for node: v_verticadb_node0008 
 WARNING: Target node v_verticadb_node0008 is down, so depot size has been 
          estimated from depot location on initiator. As soon as the node comes
		  up, its depot size might be altered depending on its disk size
Eon database detected, creating new depot locations for newly added nodes
Creating depot locations for 1 nodes
 Warning when creating depot location for node: v_verticadb_node0009 
 WARNING: Target node v_verticadb_node0009 is down, so depot size has been 
          estimated from depot location on initiator. As soon as the node comes 
		  up, its depot size might be altered depending on its disk size
Cloning subcluster properties
NOTICE: Nodes in subcluster analytics_1 have network addresses, you 
might need to configure network addresses for nodes in subcluster 
analytics_2 in order to get load balance groups to work correctly. 

	Replicating configuration to all nodes
	Generating new configuration information and reloading spread
	Starting nodes: 
		v_verticadb_node0007 (10.11.12.81)
		v_verticadb_node0008 (10.11.12.209)
		v_verticadb_node0009 (10.11.12.186)
	Starting Vertica on all nodes. Please wait, databases with a large catalog 
	     may take a while to initialize.
	Checking database state for newly added nodes
	Node Status: v_verticadb_node0007: (DOWN) v_verticadb_node0008: 
	             (DOWN) v_verticadb_node0009: (DOWN) 
	Node Status: v_verticadb_node0007: (INITIALIZING) v_verticadb_node0008: 
	             (INITIALIZING) v_verticadb_node0009: (INITIALIZING) 
	Node Status: v_verticadb_node0007: (UP) v_verticadb_node0008: 
	             (UP) v_verticadb_node0009: (UP) 
Syncing catalog on verticadb with 2000 attempts.
	Multi-node DB add completed
Nodes added to subcluster analytics_2 successfully.
Subcluster added to verticadb successfully.

Re-running the queries in the first part of the example shows that the settings from analytics_1 have been duplicated in analytics_2:

=> SELECT name, subcluster_name, memorysize FROM SUBCLUSTER_RESOURCE_POOL_OVERRIDES;
 name | subcluster_name | memorysize 
------+-----------------+------------
 tm   | analytics_1     | 0%
 tm   | analytics_2     | 0%
(2 rows)

=> SELECT name, subcluster_name, memorysize, plannedconcurrency 
       FROM resource_pools WHERE subcluster_name IS NOT NULL;
      name      | subcluster_name | memorysize |  plannedconcurrency 
----------------+-----------------+------------+--------------------
 analytics_pool | analytics_1     | 70%        | 8
 analytics_pool | analytics_2     | 70%        | 8
(2 rows)

=> SELECT * FROM LOAD_BALANCE_GROUPS;
   name    |   policy   |  filter   |    type    | object_name 
-----------+------------+-----------+------------+-------------
 analytics | ROUNDROBIN | 0.0.0.0/0 | Subcluster | analytics_2
 analytics | ROUNDROBIN | 0.0.0.0/0 | Subcluster | analytics_1
(2 rows)

As noted earlier, even though analytics_2 subcluster is part of the analytics load balancing group, its nodes do not have network addresses defined for them. Until you define network addresses for the nodes, Vertica cannot redirect client connections to them.