You can check your Macintosh System Profile. When you select the installed eSATA card, the Device ID will show either "0x6081" or "0x5081". The 3 Gigabit/second eSATA cards use the Marvell chip 88SX6081. The 1.5 Gigabit/second eSATA cards use the Marvell chip 88SX5081.
Macintosh bootable volumes are supported on the internal 2-port PCI card (part number TSATA) but are not supported on any of the other SATA cards at this time.
Our testing has shown that a four-drive array will sustain maximum reads and writes of about 200 MB/second in a 64bit, 33MHz PCI slot. An eight-drive array will not provide any additional performance beyond that of a four-drive array in that slot. To get significantly more performance, you need to use a machine with a PCI-X slot.