It is possible to add High Speed eSATA ports to all of the following Macs:
Powermac G4 and G5 Series
Mac Pro
Macbook Pro
Powermac G4 & G5 with Available PCI Slot:
4 Port PCI-X Card:

System Requirements:
Available PCI-X / PCI slot. Mac OS X v10.3.9 or later / Windows 2000, Windows XP
Powermac G5 and Mac Pro with Available PCI-Express Slots:
2 Port eSATA PCI-Express Card:

System Requirements:
Available PCI-Express (x1) slot. Mac OS X v10.4.5 or later / Windows 2000, Windows XP
2 Port eSATA Extender Cable for Mac Pro:

Macbook Pro with Available Express34 Slot:
2 Port eSATA Express34 Card:
System Requirements:
Supports Windows 2000, ME, XP / VISTA ready / Mac 8.6, 9.x, 10.1.2, and above
All of the above cards provide a simple eSATA interface between external devices (like external hard drives) and the Logicboard of your Mac. If a RAID hard drive is connected via one of these eSATA cards, the RAID controlling will need to be carried out by the External RAID Drive itself (Hardware RAID), or via Disk Utility's RAID feature (Software RAID).
It is possible to install a RAID Controller card to your Mac which will allow you to connect an external multibay hard drive enclosure with no on-board RAID Controller, and perform a "Hardware RAID" via this card.
