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Lund Performance Solutions


SOS Disk I/O Summary

The Disk I/O Summary Screen

The Disk I/O Summary screen provides a summary of performance data for all disks on the system. This screen is available in graphical and tabular formats.
To access the Disk I/O Summary screen from any SOS display screen:
  • Type s from the SOS Enter command: prompt to view the Screen Selection Menu screen.
  • From the Screen Selection Menu screen, enter d (Disk I/O Summary). The Disk I/O Summary screen will display.
  • Type t to toggle between the graphical and tabular displays.
  • Examples of the Disk I/O Summary screen are provided in "Graphical Format" (next page) and "Disk I/O Summary Screen Display Items".

    Disk I/O Summary Screen Display Items

    Graphical Format

    Figure 12.1 shows an example of the Disk I/O Summary screen in graphical format.


    Figure 12.1 SOS Disk I/O Summary screen (graphical format)

    DISK I/O SUMMARY (graphical format)

    The DISK I/O SUMMARY data items are described in the following table.
    Table 12.1 SOS DISK I/O SUMMARY data items
    Data Item
    Description
    Device
    The Device column in the left portion of the graphical DISK I/O SUMMARY lists each of the disk device identification numbers.
    Percent Utilization
    The Percent Utilization graph shows the percentage of time during the interval that the device was in use.
    I/Os per second
    The I/Os per second value in the graphical DISK I/O SUMMARY represents the number of physical disk I/Os on the disk per second. Similarly to the IO/s bar graph in the Global Summary screen, specific code letters in the bar graph tell you how many of each type of physical I/Os were accumulated in the current interval. The code letters are:
  • R represents the number of physical reads per second.
  • W represents the number of physical writes per second.
  • TOTALS
    The TOTALS line shows the total utilization and disk I/Os per second for all disks.
    The tabular Disk I/O Summary screen is discussed on 113.

    Tabular Format

    Figure 12.2 shows an example of the Disk I/O Summary screen in tabular format.


    Figure 12.2 SOS Disk I/O Summary screen (tabular format)

    DISK I/O SUMMARY (tabular format)

    The data items in the DISK I/O SUMMARY portion of the Disk I/O Summary screen are described in the following table.
    Table 12.2 SOS DISK I/O SUMMARY data items
    Data Item
    Description
    Dev
    The device identification number for each disk on the system.
    I/O%
    The percentage of all disk I/Os on the system performed by each disk during the interval.
    Qlen
    The average number of disk requests waiting to be serviced by each disk.
    Util%
    The percentage of time each disk was in use during the interval.
    Wait Time (ms)
    The average number of milliseconds an I/O request had to wait in the disk queue before being serviced for each disk.
    Service Time (ms)
    The average number of milliseconds an I/O request takes to be serviced once it is removed from the disk queue and processed.
    Read Rate (/s)
    The number of physical reads from the disk per second.
    Write Rate (/s)
    The number of physical writes from the disk per second.
    Avg Size (kb) Read
    The average size of the physical reads from the disk.
    Avg Size (kb) Write
    The average size of the physical writes from the disk.
    TOTALS
    The totals for each column in the tabular DISK I/O SUMMARY.

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