Script to show if AIX Device Attributes are Actually in Effect
brian_s 270002K5X3 Comments (2) Visits (5760)
There are several storage related settings in AIX that cannot be changed if the device is active. These include "fast_fail" , Dynamic tracking (dyntrk), and the "num_cmd_elems" for HBA's and the Queue Depth for hdisks.
Your options to set these are either make the device inactive (usually by taking redundant paths offline) and then make the change, or to use the "-P" flag on chdev and then reboot the server to make the change effective at the next boot.
The "-P" option on chdev has one major drawback however. As soon as you make the change with chdev "-P" it appears that the setting is active right away even before the reboot. If you check with "lsattr" it will appear as if the setting has taken effect. However it actually won't take effect until the next reboot. What has essentially taken place is that the running configuration is out of sync with the ODM. The ODM reflects the updated settings, however they can't be changed in the running configuration of the AIX kernel until the next reboot.
Until recently, the only way to really verify if these kinds of attributes were actually active was to check in KDB. Last year I even wrote a script that would check this in KDB and report differences (see post: Scri
Very recent versions of AIX have made a major improvement to "lsattr" where you now have a "-P" flag to show what is actually currently active. Chris Gibson did a very good write up on this on his blog (see his post: Than
I wrote a script that will go through every device on your AIX server and compare the "lsattr -Pl" (running config) versus "lsattr -El" (ODM config) and show you all devices that have differences. If the script finds any differences it will show you which attributes are different between the ODM and the running configuration. If everything is in sync then there isn't any output.
Since the script relies on "lsattr -Pl" you must be at AIX 6.1 TL9 or AIX 7.1 TL3 or later for this script to work! If you are running an older AIX version check out my previous script that uses KDB (Scr
Here is some example output from the script that shows fcs0's num_cmd_elems and hdisk0's queue_depth attributes are changed in the ODM but not on the running/active system. The ODM configuration for num_cmd_elems is 199 but the running configuration is 200. Likewise, the queue depth ODM configuration is 19 but the running configuration is 20.
Here is the script (again, note that it needs AIX 6.1 TL9 or AIX 7.1 TL3 or later to work):