This is the first time I had got to evaluate one of Synology's expansion unit, and the verdict was absolutely positive. High-end NAS servers like the DS1515+ can take up to two DX513 expansion units, which is enough to cover the huge capacity a company might needs. Connecting it to a Synology NAS is straightforward, and its disks are controlled directly in DSM since the NAS sees the DX513 as a part of its own hardware. The only downside is the DX513's very high price, and it shouldn't be as pricey since its hardware is simple and doesn't utilize any expensive components that could raise production cost. I would also like it to come with a longer eSATA cable since the one it does come with is really short. I would have liked the DX513 to come with metallic HDD trays with vibration-absorbing material, which the DS1515+ NAS doesn't feature either.

The DS1515+ is a powerful, efficient NAS that runs an excellent OS (DiskStation Manager, or DSM) with a ton of functionality. Its Rangeley CPU is supported by 2 GB of RAM and performs very well in most situations; however, the lack of Intel's Quick Assist technology leads to a notable drop in speeds with encrypted file transfers. Synology should also equip this NAS with at least 4 GB of RAM given it is for business environments, and its 2 GB DIMM limits the maximum amount of RAM to 6 GB because a normal user won't get to that occupied RAM slot to replace that 2 GB DIMM with a 4 GB stick, which would, incidentally, also void the product's warranty because you have to take the mainboard out. I think a USB port in front would have been nice as well, but Synology preferred to install all of them into the rear. The lack of an HDMI port might be fine in a business setting, but such a port might even be useful to an IT admin as it allows for the NAS to be used without a client PC.

Like its big brother, the DS1815+, the five-bay DS1515+ performed very well, and I am pretty sure it will completely satisfy users or companies that procure one. You should take into account that the 770 bucks Synology asks don't just cover the hardware's design and its components, but the software into which Synology put a great deal of time and money, which ensures DSM's current compatibility with application packages, its functionality, and reliability. However, a lower price is always welcome and obviously helps in achieving a higher price/performance ratio, although reliability and performance usually beat out cost in a business environment.