How to sync an already uploaded folder on Goggle Drive with local PC


My apology if this has already been answered, but I couldn’t find a solution through the forum search.

I need to upload and keep in sync around 50TB to Google Drive. About 15TB is locally on my machine and the remaining 35TB on a Synology NAS. InSync has now been running for around 3 weeks and only uploaded around 1TB despite being on a 500Mbit fiber connection. I am getting around 0,5-1,5 MB/s in upload, but I discovered that uploading at the same time through the Google Drive web module gives me speed of around 5-10 MB/s so around 8-10 times faster.

Because of this fact I would like to upload the files manually using the Google Drive web module maintaining the folder structure I have on my HD, and then afterwards use InSync to keep the folders in sync between Google Drive and my HD.

I haven’t found a way to do that. Is it me who is blind or is this not a current feature?

I found an old post from 2015 mentioning something similar, but the reply said it was a feature currently being worked on in '15 but no mentioning of it afterwards.

Kindly Thanks in advance.