Vijay Adik vadik@us - IBM

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IBM Advanced Technical Support - Americas
IO : Asynchronous IO (AIO) fastpath
With fast_path, IO are queued directly from the application into the LVM layer without any
“aioservers kproc” operation.
� Better performance compare to non-fast_path
� No need to tune the min and max aioservers
� No ioservers proc. => “ps –k | grep aio | wc –l” is not relevent, use “iostat –A” instead
Application AIX Kernel
Disk
• Raw Devices / ASM :
� check AIO configuration with : lsattr –El aio0
enable asynchronous IO fast_path. :
AIX 5L : chdev -a fastpath=enable -l aio0 (default since AIX 5.3)
AIX 6.1 : ioo –p –o aio_fastpath=1 (default setting)
• FS with CIO/DIO and AIX 5.3 TL5+ :
� Activate fsfast_path (comparable to fast_path but for FS + CIO/DIO)
AIX 5L : adding the following line in /etc/inittab: aioo:2:once:aioo –o fsfast_path=1
AIX 6.1 : ioo –p –o aio_fsfastpath=1 (default setting)
© 2009 IBM Corporation
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April 17, 2009