As I wrote in my last post, I had a very frustrating experience trying to use a Cavalry external disk enclosure for expanded storage on my Mac Pro. I still needed the space, though, so had to go back to the drawing board. My next step was to look for an alternative. I did some additional research, and learned the eternal SATA (eSATA) disks come in two different types of enclosures: those that use eSATA Port Multiplier technology to connect multiple disks to a single cable and those that have one cable per disk connection. During my research, I learned that Port Multiplication reduces the throughput for data transfer from the disk to the system, so I elected to purchase the Icy Dock MB561S-4S Serial ATA 3.5-Inch Multi-Bay eSATA Hard Drive Enclosure. I combined the enclosure with four Western Digital Caviar Black 1 TB Bulk/OEM Hard Drive 3.5 Inch, 32 MB Cache, 7200 RPM SATA II WD1001FALS, and a Tempo 4CH Sata II PCIe Controller Ext E4P Multiplier.
In that list you see one of the downsides: I had to put the system together myself, instead of simply buying one packaged product. Too bad.
But, it worked well. Immediately after I installed the Tempo card and booted the system, I was able to configure the disks using the software RAID on the Mac Pro. I have run the enclosure now for over a month, and it has run very well. One thing that you'll want to know is that eSATA (unlike Firewire, USB, and even internal SATA) does not provide for a power-saving mode, so the disks will not spin down. The fan on the IcyDock will always spin, as well, adding noise to your environment. You will want to keep this in mind while making your own decision.
At this point, I have enough space to store and protect my media files and other data that had been clogging my smaller and slower disks. I can recommend this configuration as a solid option for those looking to expand their storage capacity.