MEASURE_LOCATION_PERFORMANCE

Measures disk performance for the location specified.

Syntax

MEASURE_LOCATION_PERFORMANCE ( 'path'  , 'node' )

Parameters

path

Specifies where the storage location to measure is mounted. 

node

Is the Vertica node where the location to be measured is available.

Privileges

Superuser

Notes

  • To get a list of all node names on your cluster, query the V_MONITOR.DISK_STORAGE system table:

    => SELECT node_name from DISK_STORAGE;
     node_name
-------------------
 v_vmartdb_node0004
 v_vmartdb_node0004
 v_vmartdb_node0005
 v_vmartdb_node0005
 v_vmartdb_node0006
 v_vmartdb_node0006
(6 rows)
  • If you intend to create a tiered disk architecture in which projections, columns, and partitions are stored on different disks based on predicted or measured access patterns, you need to measure storage location performance for each location in which data is stored. You do not need to measure storage location performance for temp data storage locations because temporary files are stored based on available space.
  • The method of measuring storage location performance applies only to configured clusters. If you want to measure a disk before configuring a cluster see Measuring Storage Performance.

  • Storage location performance equates to the amount of time it takes to read and write 1MB of data from the disk. This time equates to:

    IO time = Time to read/write 1MB + Time to seek = 1/Throughput + 1/Latency

    Throughput is the average throughput of sequential reads/writes (units in MB per second)

    Latency is for random reads only in seeks (units in seeks per second)

    The IO time of a faster storage location is less than a slower storage location.

Example

The following example measures the performance of a storage location on v_vmartdb_node0004:

=> SELECT MEASURE_LOCATION_PERFORMANCE('/secondVerticaStorageLocation/' , 'v_vmartdb_node0004');
WARNING:  measure_location_performance can take a long time. Please check logs for progress
           measure_location_performance           
--------------------------------------------------
 Throughput : 122 MB/sec. Latency : 140 seeks/sec

See Also