OpenSolaris is a server as well as a desktop/workstation system.
e.g. OpenSolaris is used in Sun’s “open storage” hardware (thanks to ZFS and other goodies) and is also very fine in workstation environment.
Solaris 10’s code is derived from OpenSolaris code-base.
e.g. “Solaris 11” will represent some future snapshot of OpenSolaris.
OpenSolaris is more dynamic in that the hot new technologies are test driven in OpenSolaris-based distributions and when these technologies have stabilised they then enter the “Solaris X” product through patching/upgrade framework.
You do not need multiple hard discs to take advantage of ZFS.
ZFS is a new/versatile filesystem very useful for the general computing experience as well as advanced computing experience.
e.g. ZFS allows a patched/upgraded system to be easily rolled back to a previous state.
–> Say you have system A, you then upgrade it to System B. However, you find some driver/etc. in System B have compromised your system. With OpenSolaris, you are able to rollback to System A with no sweat. Here each “system” has it’s own boot environment (BE) which is selectable from OpenSolaris’ GRUB menu. BE’s can be deleted, created, etc. and a single BE represents a separate version of OpenSolaris. A BE only contains the minimal files required to boot/init an OpenSolaris session (does not clone your data) and so BE’s are relatively lightweight. A BE is automatically created after upgrading a system and this makes system upgrades easy for novice user.
Solaris/OpenSolaris has many technologies that Linux can only dream of or is trying to clone. The SunStudio developer tools are free and rock. DTrace is powerful stuff and is also accessible from programmer tools.