Wow that will be a massive upgrade! I recently went from NPM 11.0.1 to 12.1. I also have UDT, IPAM, NCM & VNQM. The product advisor showed me that I had to step through about 17 steps of upgrades to make sure each module was compatible with the other.
If you follow the upgrade advisor, you should be fine. But set aside some time, as some installs can take an hour or so.
Obviously if you start from scratch, then it will be a nice clean and easy install. Only downside I see with this is that you'll loose all historical data and you'll need to re-add everything back into your monitoring setup, unless of course you migrate the database. But do some reading up on that as I've never done it.
I believe we're still running a single server with everything on it, except the SQL databases, so I might go with a clean install since I've got a DBA handy for the database migration.
In terms of how much work it would be on your end, upgrading from the old version is likely to be a pretty complex process, I'd expect it to take most of a full day, as there are going to be several intermediate upgrades you would need to pass through. You can get a plan for most of those using the upgrade advisor here, Product Upgrade Advisor | SolarWinds Customer Portal
Although that tool only goes to NPM 12.1, for versions newer than that the upgrade installer itself will assess the environment and let you know what steps it needs to do to get up to date.
If you do decide to do a fresh install you usually want to stand up a new database from scratch though, because different changes have been made to the db over the years and you can't just point a new instance of orion at an old database and be confident that you won't end up with potentially buggy artifacts.
I've decided to run through the upgrade from my current installation to current version. The time it takes is of less concern than resources required to build all new servers and databases. All installations are in an off-line environment.
My server is: Windows 2012-R2
My DB server is: MS SQL 2012 (SP4)
I will install VNQM from scratch.
How does the below upgrade path look? Any obvious problems?
Step Product From
1 NPM 11.5 11.5.3 2 NTA 4.1 4.1.2 3 NCM 7.3.2 7.4.1 4 NPM 11.5.3 12 5 NPM 12 12.1 6 NCM 7.4.1 7.6 7 NTA 4.1.2 4.2.1 8 NTA 4.2.1 4.2.2 9 NPM 12.1 12.2 10 NCM 7.6 7.7 11 NTA 4.2.2 4.2.3 12 VNQM 4.4.1