It's assumed that ZFS is the main file system.
For me there's simply no good reason otherwise.
ZFS is not perfect but it's way much better than UFS.
And it's mature enough to go into production.
But you have to adhere to best practices.
Again I'm assuming an ordinary standard installation of Solaris.
I'm not considering, for example, Cluster or third-parties add-ons.
In general a 2-way mirrored root pool (rpool) will be used for everything.
Certainly, for many other scenarios it's best to use additional pools.
