SirDice said:No, it's not possible to create one from sysinstall. You shouldn't use sysinstall any more, it's been deprecated.
Setting up a ZFS mirror might be a little easier. But either way you are going to have to put some effort in.
olav said:I've found a solution that is easy and works great, by using graid.
All you have to do during installation is the following.
Step 1:
Select shell when the FreeBSD installer starts.
Step 2:
Type in this command
[CMD=""]graid label ddf gm0 raid1 ada0 ada1[/CMD]
Step3:
Type [CMD=""]exit[/CMD] to return to the installer.