HP-UX HB v13.00 Ch-22 - Performance and Tuning

HP-UX Handbook – Rev 13.00 Page 16 (of 19)
Chapter 22 Performance & Tuning
October 29, 2013
 round_robin: Appropriate when all the paths to the device have similar I/O turn-
around characteristics.
 least_cmd_load: The LUN path with the least number of active I/O requests is
selected to execute the next I/O. This policy is appropriate when the paths to the LUN
exhibit asymmetric latency characteristics. The load is distributed to optimize the
bandwidth on each LUN path.
 cl_round_robin (cell aware round robin): This load balancing policy is applicable to HP
cell-based platforms. The LUN paths are selected in a round robin manner within the
locality of CPU on which the I/O was initiated, to ensure that memory access latencies
are optimized.
 preferred_path: The I/O path set in the preferred_path attribute is preferrably used for
I/O transfer. If this I/O path is not available or if the preferred_path attribute was not set,
any other path is selected for I/O transfer. This policy is useful for certain disk arrays,
which may exhibit some performance degradation if I/Os are transferred via several I/O
paths to a LUN simultaneously.
CPU
Once we have determined that the memory resources are adequate, we need to address the
processors. We need to determine how many processors there are, what speed they run at and
what load they are under during a variety of system loads .
To find out cpu load on a multi-processor system, run :
example: sar –Mu 5 100
This will produce 100 data points 5 seconds apart.
The output will look similar to :
11:20:05 cpu %usr %sys %wio %idle
11:20:10 0 1 1 0 99
1 17 83 0 0
system 9 42 0 49
After all samples are taken an average is printed
This will return data on the cpu load for each processor:
cpu - cpu number (only on a multi-processor system and used with the -M option)
%usr - user mode
%sys- system mode
%wio - idle with some process waiting for I/O
(only block I/O, raw I/O, or VM pageins/swapins indicated)
%idle - other idle
The %wio is a subset of idle time. The data for the metric is collected during a clock tick. The