3Ware 9550SXU-12 User Guide - Page 265
Drive Performance Monitoring, Types of DPM Statistics, Available DPM Commands
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Drive Performance Monitoring Drive Performance Monitoring When one drive in a RAID unit is responding much slower than others, it reduces the performance of the entire unit. Drive Performance Monitoring (DPM) is now available to measure drive performance, and to help identify when a specific drive is causing problems so that you can have the drive manufacturer repair or replace it. DPM is an advanced trouble-shooting tool. Commands are available through the 3ware CLI to enable and disable DPM, and to see a range of different statistics. These statistics can be useful to AMCC technical support to help you troubleshoot problems with your RAID controller and units. Types of DPM Statistics The following drive statistical data can be stored and reported: • Queue depth, which indicates the number of read/writes that are currently outstanding. • IOP, which indicates the number of read/writes that have completed • Transfer rate, which indicates the number of sectors that have been read/ written • Response time, which indicates the execution time of all commands • Command read/writes, which indicates the drive and drive sectors' accumulated read and write commands. Available DPM Commands Drive Performance Monitoring commands are available through the CLI. An overview of the commands is provided below. For more information about the command syntax and for examples of the report output, see the CLI Syntax Reference in the 3ware SAS/SATA RAID Controller CLI Guide. • Enable DPM. This starts the collection of statistics for drives attached to your RAID controller. (/cx dpmstat=on). For efficient collection of data, initiate read/write activity on the specified controller. The numbers will change over time as the new and old data are averaged. • Disable DPM. This stops the collection of statistics. (/cx dpmstat=off) DPM is disabled by default since there is overhead in maintaining the statistics. DPM is also disabled following a reboot or power-on. Turning off DPM does not clear the statistical data that has been recorded. To clear the data, use the command /cx/px set dpmstat=clear [type=ra|lct|ext]. www.3ware.com 253