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 identification number of the device file that corresponds to the disk.
Percent Utilization	The percentage of time the device was in use during the interval.
I/Os per second	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 defined in "IO/s".
TOTALS	The TOTALS line shows the total utilization and disk I/Os per second for all disks.

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.