SATA drive enclosures- unless they are sophisticated designs containing circuitry and controllers for advanced RAID levels - - consist basically of a place to mount drives, supply them with power and cool them. They do not contain bridge circuits, as do FireWire enclosures. A PCI card installed in the computer supplies the circuitry that controls the drives and connects them to the computer. PCI cards have various capabilities. Those from Firmtek, for example, provide separate channels for each drive and are compatible with running the drives as separate drives (JBOD = just a bunch of drives) or combining them into RAID Level 0 (striping) or Level 1 (mirroring). One could, for example, structure a 4 drive setup so that two drives were running as RAID 0 and two drives were either running as separate drives (JBOD) or as a mirror for the RAID 0 drives. More complex setups are possible with cards from other companies such as Highpoint whose cards enable RAID 5 as well as RAID 0 and 1. (RAID 5 - which combines striping and mirroring, has the advantage of being able to rebuild itself if any one drive fails.)RAID 0 is the fastest form of RAID but also provides the least data security. If, for example, one had a 4 drive RAID 0 setup, it would theoretically be able to read and write data at 4 times the speed of any one of its component drives. However if only one drive fails all the data is lost.
In addition to these basic functions, drive enclosures differ in their features, some allow easy hot-swap capability - that is, each drive is fastened to a sled that can be withdrawn from the drive enclosure while the drive is turned on (of course this won't work if all the drives are part of a RAID 0 configuration), some have larger power supplies, more effective cooling systems, temperature indicators and alarms, digital readouts of drive conditions, some use the new Infiniband connector system which enables one cable to connect from an Infiniband equipped card to multiple drives in an Infinband equipped enclosure.
Looking at what is available, it appears to me that the Mini G enclosures are vastly overpriced as they lack features that other products have at the same or lower price level. For example the Firmtek SeriTek/2eEN4 is cleverly designed so that it has no internal wiring: the drives plug in to sleds which, in turn plug into the enclosure’s back pane, the enclosure has heat sensors and indicators, two fans and a sufficient power supply to run 4 Seagate drives. MSRP is $399.95. You can check this out at
http://www.firmtek.com/seritek/There are also various hot-swap capable enclosures available from Granite Digital at
http://www.granitedigital.com/
High point makes both RAID 5 capable cards some with eSATA connectors and one with an Infiniband connector and an Infiniband capable 4 drive enclosure which costs about $440 at newegg.com.
You can checkout Highpoint products at
http://www.highpoint-tech.com
If you want the least expensive SATA drive enclosure you might look at the Mercury Elite dual SATA drive enclosure available at Other World Computing at
http://eshop.macsales.com/
This enclosure appears to have about the same feature set as the Mini G enclosure but costs $79.95 and is capable of running two Seagate (or any other) drives. (OWC is a good source of bare drives, drive enclosures and RAM at reasonable prices.)
A new and interesting technology is available from Sonnet Technologies
http://www.sonnettech.com/
This involves cards (available as mentioned above, in both PCI-X adn PCIe versions) and an enclosure (Fusion 5000) that employ "port multiplier" technology. With these cards and the 5 drive Fusion enclosure, it is theortetically possible to run as many as 20 drives with one card.
A word about Seagate drives: their published specifications indicate that they do require more power at startup than Hitachi, Western Digital or Maxtor drives (2.8 amps vs. 1.8 amps) – which is evidently why they are not recommended for use in the Mini G enclosure. This same characteristic means that they cannot be successfully used with the internal mounting brackets such as the G5 Jive bracket from Sonnet or similar brackets made by other companies. (The Mac’s power supply can’t handle the additional power demands of these drives.) On the other hand Seagate drives carry a 5 year warranty rather than the 3 year warranty given by the other manufacturers and their “Softsonic” technology makes them relatively quiet. Mounted in an enclosure with adequate power they work just fine.
SoftRaid software might be of interest to Mac users as it allows one to implement complex RAID schemes which combine RAID 0 and RAID 1. I have not used it personally but it has a very good reputation for reliability.
To learn more about this product check out:
http://www.softraid.com/
Finally you might want to check out tests of drives, PCI cards and enclosures at http://www.barefeats.com (Acording to their most recent tests (March 10, 2006), the fastest 500GB drive currently available is the new one from Western Digital).
I hope this helpful.