The root pool disk requirements for SPARC based and x86 based systems are as follows:
The disk must either be a single disk or part of a mirrored configuration. Non-redundant configurations and RAIDZ configurations are not supported for the root pool.
All subdirectories of the root file system except /var that are part of the OS image must be in the same dataset as the root file system.
All Oracle Solaris components except the swap and dump devices must reside in the root pool.
For a root pool disk that is VTOC labeled, you must create a disk slice with the bulk of disk space in slice 0 if you need to replace a root pool disk.
For a pool to be efficient, do not use different slices on a disk to share among different operating systems or with a different ZFS storage pool or storage pool components.
Oracle Solaris installs an EFI (GPT) label for the root pool disk or disks on most x86 based systems and on SPARC based systems with updated GPT firmware. However, the SMI (VTOC) label is still available and supported.
If your SPARC based system's firmware is not updated for GPT support, you must create a disk slice for a disk that is intended for a ZFS root pool. However, on x86 based systems with a root pool disk that is labeled with EFI, the correct boot partitions are created automatically.