You may be well-served to review the server requirements from the Solarwinds Support page. Check out the requirements for each product. NPM and NCM can be installed on the same server using the same SQL database, but I recommend ensuring you're using SQL 2016, since other modules (like NTA) require it.
A starter page for NPM links to server requirements: NPM Installation Guide - SolarWinds Worldwide, LLC. Help and Support
LEM installation requirements: LEM system requirements - SolarWinds Worldwide, LLC. Help and Support
I don't use LEM, and can't speak to whether it can run on the same server as NPM and NCM.
For HA, are you looking at true standby server redundancy, or simply using MS NIC Teaming or using LACP for connecting a single server to multiple switches (so a switch can fail or be taken out of service for upgrades/maintenance or replacement)?
If you're looking for true HA, you haven't mentioned purchasing HA. You should take that up with your Solarwinds Sales Engineer for advice and pricing.
Your local system administrators should provide recommendations and information about what RAID flavors are available to your hardware. If you have the option, I've had great success using VM for my Solarwinds servers. It's fast and flexible, V-Motion allows easy transfer of Guests between Hosts, and V-Snapshots make for fast and easy backups and restores.
first of all thank you a lot for your gentle reply.
I'm obliged to install all modules (NPM, NCM and LEM) and SQL Standard database on same server (I've only two server for the NMS solution and so I cannot dedicate one of these for DB only).
With these two server I've to reach ORION HA through the relative function we can find in "Product Specific Settings" area. So, I've just to configure the HA of the SQL DB using one of the HA replication solution offered, like SQL Always ON.
I'd like to have your opinion about this kind of solution, if you have any suggestion and/or warnings about. Thank you.
I think your special needs require you to contact your Solarwinds Sales Engineer at a minimum, and engage the Solarwinds Technical Support staff so they can understand your restrictions. They'll provide the best advice, and guide you to the right solutions.
They'll be able to tell you if what you want to do is possible within the limitations you've defined. And they can give you great advice that will ensure your deployment is smooth and trouble-free, if they support the environment to which you are limited.