FreeBSD 11 and Perc H720P Mini raid controller

I had a problem with my 3 latests R430 Dell server which all have a PERC H730P Mini raid controller. The installer could barely works and slowly, and 2 servers were booting and crashing with FS corruption while the latest just didn’t boot and the raid was cleared.

It is a problem with a driver of the raid controller. I don’t understand exatly the problem but I found a fix.

From man page mfi(4)

A tunable is provided to adjust the mfi driver's behaviour when attaching
to a card.  By default the driver will attach to all known cards with
high probe priority.  If the tunable hw.mfi.mrsas_enable is set to 1,
then the driver will reduce its probe priority to allow mrsas to attach
to the card instead of mfi.

In order to install the system, you have to set hw.mfi.mrsas_enable=1 on the install media, and set this on the installed system before booting it.

There are two ways for that:

• if you use a usb media, you can mount it and edit /boot/loader.conf and add hw.mfi.mrsas_enable=1
• at the boot screen with the logo freebsd, choose 3) Espace to boot prompt, type set hw.mfi.mrsas_enable=1 and boot

You will have to edit /boot/loader.conf to add the line on the installed system from the live system of the installer.

I have been struggling a long before understanding the problem. I hope this message could save time to somebody else.