For USB 2.0 and eSATA expandability (as well as Firewire800), users must purchase the DroboPro or Drobo S, both of which are direct-attached storage devices, not NASes. The Pro FS also does not have USB or eSATA ports. However, compared to other NAS boxes in its class, it's lacking in a lot of features, such as IP camera support, an easy way to setup remote access, integration with Windows Active Directory or ACLs and a full roster of third-party apps to extend its functionality.
There is no question that the Pro FS is a strong sentry for data. I pulled drives out while media files were streaming installed drives of varying capacities mixed 2.5" with 3.5" SATA drives-I did everything that could possibly damage my data or prevent the array from rebuilding, short of setting the drives on fire-and my data remained intact. It's expensive, yes, but the BeyondRAID technology works flawlessly–better than just about any other storage RAID array I have tested. Bundled with 8TB in drives, that price jumps to $2,699 and for 16TB $,3299, so this is not a cheap storage option for a small business. At a list price of just under $1000, the DS 1511+ is also half the cost of of the Pro FS, which lists for $1,999 without drives. If you're looking for a NAS that can multitask as an e-mail, print, or surveillance camera server, you'd be better off considering Editor's Choice winning Synology DS1511+ ($900, 4.5 stars), which can handle these tasks and more.
If data protection, disaster recovery, and simple file sharing are all you need in a NAS, the DroboPro FS is a very good option for a business. The DroboPro FS NAS is great at one thing: protecting your data with Drobo's proprietary BeyondRAID technology.