Marge two Vertica clusters

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  Adrian_Oprea_1

  February 2016

  So you wana decomision on Vertica Cluster and reuse the hosts in ass new nodes for the left cluster ? 

   

  Before you add any new nodes you need to

  1. Disable local segmentation(for better performance)

  SELECT DISABLE_LOCAL_SEGMENTS();

   2. Purge your data.(less work to be done during the rebalance).

  --look for delete vectors

  SELECT schema_name
            ,projection_name
            ,count(*) num_ros
            ,sum(total_row_count) num_rows
            ,sum(deleted_row_count) num_deld_rows
            ,sum(delete_vector_count) Num_dv
            ,(sum(deleted_row_count) / sum(total_row_count) * 100)::INT por_del_rows
  FROM storage_containers
  WHERE node_name = ( SELECT local_node_name())
  GROUP BY 1, 2
  HAVING sum(deleted_row_count) > 0
  ORDER BY 5 DESC;

   3. Drop any unused projections(less work to be done during the rebalance).

  - i use this sql to look for such

  SELECT
      p.table_schema,
      p.basename                                 AS "Table Name",
      MAX(pu.last_used)                          AS last_used,
      extract(DAY from (getdate()-MAX(pu.last_used)))        AS days_last_used,
     -- extract(DAY FROM GETDATE() - pu.last_used) AS "Days without Using",
      ROUND(SUM(sc.used_bytes/ (1024^2)),3.0)    AS used_mb,
      ROUND(SUM(sc.used_bytes)/( 1024^3),3.0)    AS used_gb
  FROM
      (
          SELECT
              projection_oid,
              MAX(TIME) AS last_used
          FROM
              v_internal.dc_projections_used
          WHERE
              table_oid IN
              (
                  SELECT
                      table_id
                  FROM
                      v_catalog.tables
                  WHERE
                      NOT is_system_table)
          GROUP BY
              projection_oid) pu
  JOIN
      (
          SELECT
              oid,
              name,
              basename,
              "schemaname" AS table_schema
          FROM
              v_internal.vs_projections) p
  ON
      p.oid = pu.projection_oid
  JOIN
      (
          SELECT
              projection_id,
              used_bytes
          FROM
              v_monitor.storage_containers) sc
  ON
      sc.projection_id = pu.projection_oid
  GROUP BY
      p.table_schema,
      p.basename
  ORDER BY
      last_used ASC ;
  
  

   

   4. Optimize your REFRESH resource pool for the rebalance task.

  - see if you can increase the PLANNEDCONCURRENCY value for this pool, will improve prerformance.

  and after rebalance you can put it back to default.

   

   

  To add a new node to an existing Vertica Cluster :

   

  1- Make sure you have a host with the same operation system installed as the running Vertica O.S.

  2- Prepare the box to receive  Vertica software and create the same O.S. layout(partitions).

  3- Setup the sshd password-less for root user between the two hosts(running and the host that will be added)

  3- Choose the way you want to add the new host to the cluster

  A – Using Vertica Management Console.

  B – Using the update_vertica utility.

  -- run this from one of the nodes that are part of the receveing cluster (as root user)

   

  /opt/vertica/sbin/update_vertica --add-hosts host_name1,host_name2 --rpm /tmp/vertica-version 7.x.x

  Once done - list avilable nodes in the cluster

   

   

  admintools -t list_host

  - his command will list all hosts and not all nodes.

   

   

  This will show you all nodes the run the db

   

   admintools -t list_allnodes

  Add the hosts to your db 

   

   

  admintools -t db_add_node -s host_name1,host_name2 -d database_name -p password

  Rebalance the data to apply to your required K-safety

  admintools -t rebalance_data -d <db_name> -p test -k 0,1,2

   

   

  1. Do I need to uninstall Vertica from the DR site before I'm adding the nodes to the production site? or I need only to drop the existing database on the DR site?

   - i would do a clean install

  
  2. How it's work with the downtime when I'm adding the nodes? There will be downtime? Can I still work with the production environment while I'm adding the nodes (at the re-balancing time)?

  - no downtime is required(some lock might happen on the tables), it`s just resource intensive so ideal is to do it when you less have access to the db.

  
  3. Can I add 10 nodes together? or I need to add them in batches, 5 nodes each time for example?

  - i sudgesst doing in two nodes at a time. Or actually i don`t think i know the right answer, never added more then 2 at a time in the past so i don`t actually know ! 

  
  4. What is the overhead on the system?

  - it is resoirce intensive as you basecly replicate the objects across the cluster.(network perf will impact the times if network is slow)

  vioperf: Measures the speed and consistency of your hard drives.

  vnetperf: Measures the latency and throughput of your network between nodes.

  
  5. How can I determent the re-balancing time?

  What do you mean ? 

     How long is going to take ? (it all depends on size/number of projecitons/Disk speed/Network latency)

  or 

   When should i do it ? (after you add or remove a node)

   

   

  hope this small walk thru helped you ! 

   

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  ChenSha

  March 2016

  Does anyone know if I can stop the "add nodes" command while it running?
  
  for example, if it takes to much time and it start to overhead on the system and I want to stop the process... can it be done?
  
  thanks

  0