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Full Discussion: IBM AIX I/O Performance Tuning
Operating Systems AIX IBM AIX I/O Performance Tuning Post 303031400 by bakunin on Wednesday 27th of February 2019 10:09:27 PM
Old 02-27-2019
There are two things i noticed which might affect performance negatively:

Quote:
Originally Posted by c3rb3rus
Code:
# lsattr -l fcs0 -E
max_xfer_size 0x100000   Maximum Transfer Size                              True

You can increase this to help especially larger transfers. Use the -R switch of lsattr to see legal values you can use.

These two:
Quote:
Originally Posted by c3rb3rus
Code:
# lsattr -El hdisk2
algorithm       fail_over                                           Algorithm                        True+
reserve_policy  single_path                                         Reserve Policy                   True+

are also not optimal. Basically the multipath drivers (can) use multiple pathes (FC connections from the LUN to the system) at once. These multiple pathes can be used for two purposes: the first is redundancy, so that if one connection fails it uses another. Connection failure - temporarily - happens rather frequently for reasons i don't fully understand in FC-connections. The other purpose multiple pathes can be used to is performance: using several pathes in parallel speeds things up. This is basically controlled by using the "algorithm" property. I have no test system at hand to tell you the value you need to use but there are only two of them and you need the other one - again, use the lsattr -R switch to list all legal values for the property.

The reserve_policy should be "no_reserve" but this matters mostly in clusters where disks are accessed from several systems at once.

I hope this helps.

bakunin
 

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LEARN ABOUT NETBSD

pmc

PMC(1)							    BSD General Commands Manual 						    PMC(1)

NAME

     pmc -- performance-monitoring counter interface for command execution

SYNOPSIS

     pmc -h
     pmc -C
     pmc -c event command [options ...]

DESCRIPTION

     pmc is a means of using a processor's performance-monitoring counter (PMC) facility to measure various aspects of a program's execution.  It
     is meant to be used in a fashion similar to time(1).

     The arguments are as follows:

     -h      Display a list of performance counter events available on the system.

     -C      Cancel any performance counters that are currently running.

     -c event
	     Count the event specified by event while running the command.

DIAGNOSTICS

     PMC support is not compiled into the kernel  Performance-monitoring counter support has not been compiled into the kernel.  It may be
     included using the PERFCTRS option.  See options(4) for details.

     PMC counters are not supported by CPU  Performance-monitoring counters are not available for the CPU.

SEE ALSO

     time(1), options(4)

HISTORY

     The pmc command first appeared in NetBSD 1.6.

AUTHORS

     The pmc command was written by Frank van der Linden <fvdl@wasabisystems.com>.  The kernel support for reading performance counters on the
     i386 architecture was written by
     Jason R. Thorpe <thorpej@zembu.com>.

BUGS

     The pmc command currently only supports performance-monitoring counters on the i386 architecture.

BSD
								 October 24, 2000							       BSD
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