Your performance will be lower because you are limited by your network. Gigabit ethernet is limited to 100 to 110MB/s. You probably get 3X that with an internal RAID controller.
Thanks, kanewolf. Does this mean that Synology's numbers (369 to 443 MB/s) https://www.synology.com/en-us/products/performance#5_10bay
are theoretical because there's no way to actually get the data out of the NAS any faster than 100-110MB/s ?
I don't believe you can connect a DS1515 to your computer via eSATA. It has an eSATA port to connect external storage to the Synology, but it does not provide client connectivity via eSATA.
Thanks, hadn't realized that.