Cheers guys,
All new to linux, I bought some hardware to run a little home server. I tried to install with the integrated Raid of the motherboard, but the installer doesn't see the ssd's, if I try to use software Raid, which I read is great, I can't manage to get past the partitioning to the installation....

Motherboard is a MSI B450 https://www.msi.com/Motherboard/B450M-A-PRO-MAX, tried to follow this https://www.youtube.com/watch?v=IWiXBCaBr_o but can't partition the same way, it reacts differently than in the video and the "Creat softwareRaid md option greys. By the way, it creates a /boot/efi 512Mo fat32 partition I did not ask for....

Should I try to find compatible drivers for the hardware raid ? I tried but not luck for now.

Any advice appreciated

Cheers guys

Are all of the drives you have empty and unformatted or do you have partitions/filesystems already exisiting?
The efi partition was created because you booted in efi mode and apparently, there was no efi partition on any of the drives. That should not be a problem with a RAID configuration. Never used RAID myself so can't help with that.

A quick look at that video indicates it is for a guest install on VMWare, not an install on the real hardware. Useless if you want to do the latter.

Installers are complicated code, but also pretty dumb - if the developers don't include the support, it can get pretty ugly. RAID is so ubiquitous these days, this shouldn't be hard to do. I don't use Ubuntu, but all I could find was this. Looks way too complicated for what should be a relatively simple setup.
For a new user, I might be inclined to just do a "normal" install onto one of the SSDs (/dev/sda) then convert the running system later to RAID1 across the two SSDs when you are a bit more comfortable with Linux. How complicated that gets depends on how the install was implemented - whether on LVM, separate /boot, any encryption, ... lots of potential snags.

Nothing is ever as simple as it first seems.

Your hardware RAID is what is often called a fake RAID and is not recommended for several reasons. It will create proprietary data structures on your disks, and should your motherboard fail, it is not certain that the motherboard vendor will have products that can access your data or will provide support at all. It lacks a few attributes that are essential to real hardware RAIDs, like electrical power backup or the ability to restructure your RAID.

MD RAID doesn't suffer from lack of support and has the attributes of real hardware RAIDs, with the obvious exception of a power backup.

Why the Ubuntu 18 installer disables your MD RAID option, I can't tell, but askubuntu has what looks like a nice overview of the process: https://askubuntu.com/questions/1066...with-uefi-bios.

By the way, I suppose it should be possible to use LVM's built-in mirroring instead of MD RAID. Probably easier to use. I don't know whether the installer offers this option, and I have not tried it with a root disk, but after the installation lvconvert should be able to turn an unmirrored logical volume into a mirrored one.

LVM now does true RAID1 rather than just mirror, and I find it much easier to manage, but adding the vagaries of LVM to the mix for a new user might be overwhelming.
Given this a server install, CentOS might be a better choice - and has supported LVM functionality better and for longer. And the documentation ffrom Redhat is awesome.