You won't find any network storage device that offers more space than the recently reviewed five-bay DS1511+ NAS server from Synology.
This is the first NAS we've reviewed that has up to 15TB of storage space out of the box, by supporting the new 3TB hard drives. On top of that, when used with two DX510 expansion units, the server's storage space can be scaled up to be 45TB. With front-facing drive bays, it's easy to replace or add more hard drives to the systems.
Synology DiskStation DS1511+
Apart from standard RAID configurations, the DS1511+ also offers Synologoy Hybrid RAID, which is similar to RAID 5, that allows you to add/upgrade hard drives to the system without building the RAID setup from the beginning, hence retaining the existing data. And then after that, if 45TB still isn't not enough, you can use the four USB ports to add more.
However, its immense storage space isn't the best thing about the DS1511+. Like all servers from Synology, it comes with a vast number of features, including novelties, such as the capability to host up to 20 IP cameras, turning them into a comprehensive surveillance system that's better than most--if not all--existing surveillance DVRs on the market. It also boasts a Photo Station, which integrates a blogging engine to allow you to share photos with family and friends, as well as a Download Station, which can handle any type of downloads. Plus, the DS1511+ supports mobile devices.
The DS1511+ also shines where it matters the most: performance. The server comes with two Gigabit Ethernet ports that can be used together in the Link Aggression mode to increase the throughput speed, or in the Fault Tolerance mode for fail-safe purpose. And even when only one of the ports is used, the server tops our performance charts of NAS servers. It's the fastest NAS server we've seen so far.
For more information on why the server is worth every penny of its $900 price tag (no extra storage included), check out the full review.