A couple of practical, OS X-specific, points: with current Macs, it's obvious one must go the Thunderbolt route. With older systems, however, the only affordable direct-attached-storage (DAS) solution is to use eSATA, and OS X supports ASM1061-based chipsets (found in sub-$100 PCIe cards) out-of-the box. Firewire, as we all know, is dead, and USB just doesn't cut it. A second- (or third-) tier backup to a NAS is also necessary, for archival purposes, but is a different story altogether. DAS (and not NAS) allows working with one's photos in, say, Lightroom, and that's what we are talking about in this post by MIke. My sense is that it's easy to manage multi-disk, directly-attached (clarify: not NAS) enclosures, but not with Disk Utility, as it's too rudimentary. Two products, one proprietary and non-free, and one open-source have been available for years: SoftRAID (google SoftRAID LLC), and OpenZFS. I use both extensively. My tribulations with all things storage, as pertaining to amateur photography, can be found at: https://lycabettus.wordpress.com (eSATA RAID mostly). The nice thing about this approach is that it's affordable, scalable (can use HDs, SSDs, 2- to 8-disk enclosures) and future-proof (running nicely since 2009 and will probably work once I can afford Thunderbolt). Hope this helps. With greetings from Athens, Xen