Tuning I/O, disks, fibre channel adapters

[zaxxon]

Hi all,

has anyone experience in tuning parameters for fibre channel adapters and disks like max_xfer_size and max_transfer?

If yes, did you change the parameters while the devices were up and running or did you do any precautions and which other parameters should or must be taken in account to these two up there?

Thanks in forward!



laters
zaxxon

 

[khalidaaa]

I'm not sure why you want to change the defaults for your FCs! and i've never done that but i can give you a clue to whether you can tune it while being used by this comment:

Tunable Parameters Type
All the tunable parameters manipulated by the tuning commands (no, nfso, vmo, ioo, raso, and schedo) have been classified into these categories: 

Dynamic If the parameter can be changed at any time 
Static If the parameter can never be changed 
Reboot If the parameter can only be changed during reboot 
Bosboot If the parameter can only be changed by running bosboot and rebooting the machine 
Mount If changes to the parameter are only effective for future file systems or directory mounts 
Incremental If the parameter can only be incremented, except at boot time 
Connect If changes to the parameter are only effective for future socket connections 
Deprecated If changing this parameter is no longer supported by the current release of AIX. 

For parameters of type Bosboot, whenever a change is performed, the tuning commands automatically prompt the user to ask if they want to execute the bosboot command. For parameters of type Connect, the tuning commands automatically restart the inetd daemon.

Note that the current set of parameters managed by the vmo command only includes Static, Dynamic, and Bosboot types.

So this depends on the tuable parameter type!

Have a look into this link:

http://publib.boulder.ibm.com/infoc...=/com.ibm.aix.files/doc/aixfiles/tunables.htm

Regards,
Khalid

 

[zaxxon]

I know this already, but max_xfer_size and max_transfer are set by chdev, not by any of those stated above.
I would change them to test if there is a throughput gain in some backup issue, but only as last option.

laters
zaxxon

 

[khalidaaa]

zaxxon,

I think you will need to reboot the system once you change the max_xfer_size as indicated here:

http://publib.boulder.ibm.com/infoc...ric.help.doc/f2c_trbl_aixmaxtrnsf_2fhagc.html

Regards,
Khalid

 

[zaxxon]

Ok, thanks Khalid.

laters
zaxxon