MEASURE_LOCATION_PERFORMANCE

Measures a storage location's disk performance.

Measures a storage location's disk performance.

This is a meta-function. You must call meta-functions in a top-level SELECT statement.

Behavior type

Volatile

Syntax

MEASURE_LOCATION_PERFORMANCE ( 'path', 'node' )

Parameters

path
Specifies where the storage location to measure is mounted.
node
The Vertica node where the location to be measured is available. To obtain a list of all node names on the cluster, query system table DISK_STORAGE.

Privileges

Superuser

Notes

  • 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)

Examples

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