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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 REDHAT

elvtune

ELVTUNE(8)						      System Manager's Manual							ELVTUNE(8)

NAME

       elvtune - I/O elevator tuner

SYNOPSIS

       elvtune [ -r r_lat ] [ -w w_lat ] [ -b b_max ] /dev/blkdev1 [ /dev/blkdev2 ...  ]

       elvtune -h

       elvtune -v

DESCRIPTION

       elvtune	allows	to  tune the I/O elevator per blockdevice queue basis. The tuning can be safely done at runtime. Tuning the elevator means
       being able to change disk performance and interactiveness. In the output of elvtune the address of the queue tuned will be shown and it can
       be  considered  as  a queue ID.	For example multiple partitions in the same harddisk will share the same queue and so tuning one partition
       will be like tuning the whole HD.

OPTIONS

       -r r_lat
	      set the max latency that the I/O scheduler will provide on each read.

       -w w_lat
	      set the max latency that the I/O scheduler will provide on each write.

       -b b_max
	      max coalescing factor allowed on writes when there are reads pending in the queue.

       -h     help.

       -v     version.

NOTE

       Actually the only fields tunable are those relative to the IO scheduler. It's not possible to select a one-way or two-way elevator yet.

       For logical blockdevices like LVM the tuning has to be done on the physical devices. Tuning the queue of the LVM logical device is useless.

RETURN VALUE

       0 on success and 1 on failure.

HISTORY

       Ioctls for tuning elevator behaviour were added in Linux 2.3.99-pre1.

AUTHORS

       Andrea Arcangeli <andrea@suse.de> SuSE

Version 1.0							   14 March 2000							ELVTUNE(8)
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