"A well designed/unique storage device"4.5 starson by davidcw
Pros: Uses ALL the space on different harddrives from different manufacturers
Cons: Is NOT network-attached (similarly priced NAS support networked servers/applications)
Summary: I own a Drobo and 2 ReadyNAS NVs (what some would cite as a competitor). Both are great storage solutions that support automatic RAID expansion as drives are inserted. What makes the Drobo unique is its ability to USE ALL of the space on different sized drives: On every home-qualtiy NAS unit that exists today, you can stick in 2x 500GB drives and 2x 1TB drives and get 1.5 TB of RAID protected space. What happens to the remaining 500GB on each 1TB disk?... it's wasted. On the Drobo, this space is still accessible, just NOT RAID protected. This might sound like a loss, but let's say you own a NON-Drobo NAS with drive bays occupied by 500GB disks and you want to increase the storage, to do so you would need to buy FOUR** larger disks, before any RAID expansion occured.
The Drobo's firmware also supports 1TB SATA drives out of the box (and provided the LB Addressing scheme doesn't change I think* it can support even larger drives without firmware update). Currently the competitor's firmware (v3) only allows up to 750GB drives, with 1TB support promised in the next firmware release.
The Drobo's file transfer speeds are also better than the (ahem*) competitors.
A disadvantage of the Drobo is that it is NOT networked and is just a storage unit. The similarly priced ReadyNAS supports a variety of network based applications including FTP, UPnP streaming, auto USB-backup, and includes decent backup software.
Which one you should buy is up to your storage, access, and spending habits.