absolutely agree with answers from Gents above
re your concern about speed of transfer for such data samples from the PC to the NAS:
1. the internal drive:
- you have 5 specific bottlenecks
- first is the big portion of small files (what is absolutely normal from operation point of view). You will need big support from all below mentioned parts. Instead you will get really slow speed. Don’t be surprised.
- second is your PC architecture (not mentioned)
- third is a setup of your LAN (not mentioned) ... you have an option to use LACP with two 1Gps NICs in the NAS for faster transfer. Only if you have support in uour PC and LAN (switch).
- forth is the NAS itself, specially the CPU (Realtek) inside in your NAS. Because all the data handling is performed by the CPU (ethernet, sw RAID, BTRFS, ...).
-fifth - first copy will be fine. It will be pure sequential write. Next will be more complicated for your NAS CPU due the random IOPS.
Finally, used drives in the RAID. But you don’t need fast HDDs, even SSDs, because you can’t utilize them with your NAS CPU and w/o LACP.
2. the USB drive:
- it’s better to connect the drive directly to NAS
- you will get faster transfer, than through the PC
- but don’t expect a speed of light
Last point:
- you can check Syno Active backup for business (AB4B) for a comparison with the Robocopy. There are more advantage features, e.g. backup of used files, and more useful ...