Under a "short" name Mercury Elite-AL Pro Qx2, OWC manufactured an aluminum case fitting four SATA 2.0 hard drives, with capacities going between 2-8TB. What makes this product interesting to us is the fact that it features built-in cache, so this is not an amateurish product that "promises heaven and delivers hell".
Mercury Elite-AL Pro was built on Oxford 936QSE RAID chipset with 64 or 128MB of cache. Supported hard drives go all the way up to 10,000 RPM, so you can order WD VelociRaptors or install them yourself... the raw data transfer is 300MB/s and for that you really need to have four hard drives. The drives are hot-swappable, which by the way, we would not recommend doing that unless you run RAID5 ;)
Supported RAID modes are 0, 1, 5 and 10 [1+0 or 0+1] or just the regular span mode [NRAID or JBOD], and you can change them by a simple push, since the front of this RAID box includes RAID mode selector.
Beautiful Aluminum box... can it handle the heat and perform better than Apple's own RAID?
Connectivity options include a single USB 2.0 [60MB/s], a single FireWire 400 [50MB/s], two FireWire 800 [100MB/s] and one eSATA [300 MB/s] connector. Software-wise, you get Carbon Copy Cloner, ProSoft Engineering Data Backup 3, NovaStor NovaBACKUP and Intech SpeedTools Utilities. Of course, you have to pay for all of this, and prices are ranging from $680 for 2TB [4x500GB HDD] to 1900 for the 8TB part. There is also an Enterprise-Class option, consisting out of 2TB and 4TB drives [RAID0+1] for 800 and 1150 greenbacks.
All in all, OWC made an interesting product, and to make the matters funnier, cheaper one than if you would purchase RAID option on fresh Mac Pro. However, until we see one for a review, and how it performs in our own Video Production Studio handling a 4K RED RAW stream, we cannot recommend you to purchase one.
UPDATED April 15, 20:00 UTC - We received word that at present, OWC does not ship this product outside United States. Thus, you can still get it if you have somebody living in the USA and is willing to re-ship you the part.