We plan on upgrading our existing NetApp 8.1.1 (FAS3070) 7-Mode filer to NetApp 9.0 7-Mode. I know for a fact that there is no direct upgrade to NetApp 9.0 if we are running an earlier version than 8.3.X. First, you need to upgrade to NetApp 8.3.X and then upgrade to NetApp 9.0 or 9.1.
For this reason, we need to first upgrade to 8.3.X and then to 9.0 or 9.1
I have looked for KB articles and on the Internet as well but I could not find sufficient guides that guides you through NetApp 8.1.X 7-Mode upgrade to NetApp 8.3 7-Mode.
Has anyone completed such upgrade in the past? Is there any KB articles or guides available or tools available?
You can convert a system from ONTAP 7 mode to ONTAP 9 using "Copy Free Transition" - in this method, you purchase a new controller and attach the old disks to that. There are a lot of caveats and you should work with NetApp PS to perform it - but it is possible.
However, in many cases, due to increase in drive capacity or SSD performance, standing up a new ONTAP 9 system and performing data migration with the 7-Mode Transition Tool (7MTT) or Application level migrations such as Storage VMotion are likely more convenient choice.