General PerformanceThe S355BU33ERM unlike the DX517 is made by StarTech. There always other brands out there like StarTech which are often innovative. You might not get the same user experience comparing with other better known brands. But sometimes you might not need it.
About Connections One USB3 port on this StarTech is offering you up to 5Gb/s transfer speeds of external devices. It is fast enough to get your files through fairly quickly with this speed and make backing up with an external drive or Apple Time Machine a quick and easy process. There is one eSATA port on S355BU33ERM giving you up to 6Gb/s transfer speeds.
About Usage As there are no LAN ports, you probably know this is DAS (directly attached storage) box. Sometimes more than anything we need speed! If you have chosen right drives for your S355BU33ERM box, you can expect the best performance whilst you are editing your videos or working with graphics. Only disadvantage with DAS boxes, is data sharing capabilities, compared with NAS functionality.
Price And Warranty
designUsing the same chassis design that has been found in the previous NAS units and and expansion (the DX513) this new 2017 Synology unit is identical in design to it's predecessor.
featuresLacking a discernible CPU and Memory, this device does not provide any other features than adding storage - it does not feature or function independently of a connected Synology DS1517+ or DS1817+ NAS.
performanceOnce again, as this is a brainless storage box, it only performs as well as the NAS it is connected to.
valueIf you want the option to expand your NAS storage, this serves as an excellent, if slightly large solution. Let's hope a DX217 NAS expansion is released by Synology in the near future.
designIt may well look the same as a NAS, sound the same as a NAS and be the same scale as a NAS - but this is NOT A NAS! This expansion is designed for those that want to expand their existing storage. However you will need more space (physical) as well as it needing it's own power supply.
featuresIf you want this to improve your storage in ANY way other than more Gigabytes and Terabytes, you will be disappointed as it does not provide any performance improvements what-so-ever.
performanceIt will only function as an added storage volume or expanded RAID if you connect to a compatible device. So you cannot just use this device with any unit before 2017.
valueHard to justify the cost from the outset. If you plan on going big immediately, you would be better off going for an 8-Bay or larger
General PerformanceThe DX517 unlike the S355BU33ERM is made by Synology. People often choose Synology because of user friendly interface as well as being suited for Mac and Windows based environments. It is relatively easy to set up and use, and those who are new to Network Attached Storage are advised to go for the Synology.
About Connections There is one eSATA port on DX517 giving you up to 6Gb/s transfer speeds.
About Usage As there are no LAN ports, you probably know this is DAS (directly attached storage) box. Sometimes more than anything we need speed! If you have chosen right drives for your DX517 box, you can expect the best performance whilst you are editing your videos or working with graphics. Only disadvantage with DAS boxes, is data sharing capabilities, compared with NAS functionality.
Price And Warranty This box comes with 3 year warranty for your peace of mind and long term hardware security. Despite S355BU33ERM has better warranty, it is still good to know that you have your three years of no worries manufacturer cover. This is the most expensive box with the price tag £407.00.