HP-UX 11i v3 Mass Storage I/O Performance Improvements

Improved performance tracking tools
The HP-UX 11i v3 mass storage stack provides new or improved performance tracking capabilities,
including information regarding:
• Per HBA port performance
• Tape performance
• Read/Write performance
• Per lunpath performance
• Statistics at various levels of the mass storage stack
You can display the per HBA port performance data with the new –H option to the sar command, or
with new options in the GlancePlus system performance monitor. The per HBA port performance data
includes:
• I/O operations per second (IOPS) per HBA port, including read versus write breakdown
• I/O throughput per HBA port, including read versus write breakdown
• HBA port utilization %
• Average number of I/O operations outstanding to the HBA port
• Average queue time (in milliseconds) in the HBA driver
• Average service time (in milliseconds) in the HBA driver
The queue time is the time that an I/O request sits in the HBA driver waiting for resources before
being started in the hardware. The service time is the round-trip time to service an I/O request in the
hardware.
The HBA port utilization % is the percentage of time that the HBA port is “busy” with I/O requests
outstanding on it. For example, the sar –H 5 command displays in the HBA port utilization % value,
for each HBA port, the percentage of time I/O requests were outstanding on the HBA port during the
specified 5 second interval.
In addition to the new –H option, sar provides the following new command options in HP-UX 11i v3:
• L — Reports the per lunpath performance data
• R — Used with –d to add read versus write breakdown on per LUN reporting
• T — Reports tape device performance data
The iostat command provides a new option, -L, to display I/O statistics for each active lunpath.
In addition, a new command, scsimgr, provides options to display and clear a variety of I/O
statistics globally or with respect to various components in the mass storage stack (for example, HBA
ports, targets, LUNs, and lunpaths).
These new capabilities allow the system administrator to more granularly track performance at various
components and levels in the stack and to thus more readily identify hot spots and adjust the
configuration to better distribute the workload.
For additional information, see sar(1M), iostat(1M), scsimgr(1M), and glance(1).
New SCSI tunables
The following new performance-related SCSI tunables are available in HP-UX 11i v3 with the
scsimgr command:
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