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Operating Systems AIX IBM AIX I/O Performance Tuning Post 303032108 by rowswell on Monday 11th of March 2019 05:05:14 PM
Old 03-11-2019
Hi - as you can see in your results the xdisk tool with 1 MB block size drove the V7000 up to 3.4 Gigabytes per second.
The reason I mentioned using 0x40000 for the hdisk max_transfer is because that is what the SDDPCM driver used by default and I have seen better V7000 performance with this value compared to the 0x80000 default that AIX MPIO uses.
You can leave the FC adapter at 0x100000 or you could change it to 0x200000. This tunable is independent of the hdisk one.

If you do reduce the hdisk max_transfer from 0x80000 to 0x40000 you can then compare the xdisk results now that you have already run it once.

Thanks
Dean

--- Post updated at 09:05 PM ---

Regarding your question of tuning max_xfer_size you can do it dynamically assuming your LUN's have multiple paths. (lspath to confirm)
Code:
rmdev -l fscsiX -R
chdev -l fcsX -a max_xfer_size=0x200000
cfgmgr

 

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TRUNCATE(1)							   User Commands						       TRUNCATE(1)

NAME
truncate - shrink or extend the size of a file to the specified size SYNOPSIS
truncate OPTION... FILE... DESCRIPTION
Shrink or extend the size of each FILE to the specified size A FILE argument that does not exist is created. If a FILE is larger than the specified size, the extra data is lost. If a FILE is shorter, it is extended and the extended part (hole) reads as zero bytes. Mandatory arguments to long options are mandatory for short options too. -c, --no-create do not create any files -o, --io-blocks treat SIZE as number of IO blocks instead of bytes -r, --reference=RFILE base size on RFILE -s, --size=SIZE set or adjust the file size by SIZE bytes --help display this help and exit --version output version information and exit SIZE is an integer and optional unit (example: 10M is 10*1024*1024). Units are K, M, G, T, P, E, Z, Y (powers of 1024) or KB, MB, ... (powers of 1000). SIZE may also be prefixed by one of the following modifying characters: '+' extend by, '-' reduce by, '<' at most, '>' at least, '/' round down to multiple of, '%' round up to multiple of. GNU coreutils online help: <http://www.gnu.org/software/coreutils/> Report truncate translation bugs to <http://translationpro- ject.org/team/> AUTHOR
Written by Padraig Brady. COPYRIGHT
Copyright (C) 2013 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>. This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. SEE ALSO
dd(1), truncate(2), ftruncate(2) The full documentation for truncate is maintained as a Texinfo manual. If the info and truncate programs are properly installed at your site, the command info coreutils 'truncate invocation' should give you access to the complete manual. GNU coreutils 8.22 June 2014 TRUNCATE(1)
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