Regarding FreeBSD and RAID, first thing that comes to mind is surely ZFS and RAIDZ. But in some cases, good old gmirror of UFS partitions can be useful as well, for example when we want to place OS on a pair of smaller SSDs for speed, while having another set of slower SATA HDDs for ZFS storage. This article shows exact steps how to install FreeBSD in UEFI mode onto (mostly) UFS partitions residing on gmirror RAID1.