There are several things to investigate when building a NAS server:
- cpu. The RPi 3 is an improvement in clock speed over the previous ones. And Samba is a user process, and not multithreaded, so not optimized for more than one core, every client gets a new smbd (see
https://www.samba.org/samba/docs/man/Sa ... cture.html) and that may be distributed to another core if Linux decides this.
- network connection. The 100 Mb ethernet limits the theoretical bandwidth to about 10 MB. But it is doubtfull the Pi can push that amount of data from an USB disk, because:
- the way the network is connected to the system: on the Pi that is an USB connection and shared with e.g disk i/o
- disk i/o. Though the SD card is on a separate SPI bus, any other disk will be via USB 2.0 and shares the USB with the network connection
- memory to cache data. The 1 GB is an improvement over the 512 MB of older Pi's or Zero.
Of these bottlenecks the CPU and memory will have less influence than the USB bottleneck.
No wonder you were unamazed with the Pi 1 solution, and the RPI3 will only improve on CPU here.
To get more impressive performance you will need a system which has an architecture with separate and dedicated channels for I/O: native ethernet, native disk I/O like SATA. A good example are the Synology and such NAS boxes: mediocre CPU's also with modest amount of memory but better disk i/o and Gbit network channels.
A NAS such as a Synology box even the cheap ones, will outperform the RPi and come with an excellent case and excellent maintained software, up an running in minutes. Take a RPi + case + powersupply + USB to HDD interface and a couple of hours configuring the system and you will have a cheap but inferior NAS solution. The RPi is not designed for this!
