Simpler Navigation for Servers and Operating Systems - Please Update Your Bookmarks
Completed: a much simpler Servers and Operating Systems section of the Community. We combined many of the older boards, so you won't have to click through so many levels to get at the information you need. Check the consolidated boards here as many sub-forums are now single boards.
If you have bookmarked forums or discussion boards in Servers and Operating Systems, we suggest you check and update them as needed.
Showing results for 
Search instead for 
Did you mean: 


Miguel A. Velasco Corte
Occasional Contributor



How can i found out what the max_io_size is for my HPUX 11i?


Helen French
Honored Contributor

Re: Max_io_size?

Hi Miguel:

From TKB #KBRC00003661:


To tune Oracle it is required to know the maximum io transfer size. What is the maximum single io transfer size on a HP-UX system?

1) Using raw disk devices, the maximum io transfer size is 1 megabyte.

2) Using LVM (logical volume manager) the maximum io transfer size is 256

3) Using LVM with LVM striping, the maximum io transfer size is limited to the size of your strip or at most 256k.

The disk io drivers will also try to combine the requests, so it's possible to have a larger io transfer size, but since this is not easily calculated, there is no way to know what the highest io transfer size could be.

Life is a promise, fulfill it!
harry d brown jr
Honored Contributor

Re: Max_io_size?

kmtune | grep maxdsiz

shows you how much memory a process can consume. Maybe you were looking for something else?

live free or die
Live Free or Die
IT Response
Esteemed Contributor

Re: Max_io_size?


The right parameter is max_direct_iosz. This is a parameter belong to VxFS. If you want to tune it, then either using vxtunefs command or create a file /etc/vx/tunefstab, for example:

To display:

# vxtunefs -p /home
Filesystem i/o parameters for /home
read_pref_io = 65536
read_nstream = 1
read_unit_io = 65536
write_pref_io = 65536
write_nstream = 1
write_unit_io = 65536
pref_strength = 10
buf_breakup_size = 131072
discovered_direct_iosz = 262144
max_direct_iosz = 262144 <------ here
default_indir_size = 8192
qio_cache_enable = 0
max_diskq = 1048576
initial_extent_size = 8
max_seqio_extent_size = 2048
max_buf_data_size = 8192

Hope these info will help you further