If you are trying to get Gentoo Linux running on a machine with a SATA hard disk, you will either need to pass nolvm2 to the kernel at CD-boot time, or issue the command dmsetup remove_all after you’ve booted.

Otherwise, mount will frustratingly claim that the SATA-disk partitions are busy when you try to mount them after having created them and their resident filesystems with cfdisk and mkfs.

Given current hardware trends, the percentage of first-time users attempting to set up Gentoo on a SATA disk would seem likely to vastly outstrip the percentage of those needing LVM2 functionality out-of-the-box; given that, the decision to favor the former at the expense of the latter seems… ill-considered at best. But then, I wasn’t consulted.