Uploading large folders to Onedrive

I have ~300GB of photos and other data, stored on an external hard drive, that I want to put on my onedrive account. As an Office365 customer I have 1TB of storage available.

I have the Onedrive app installed on my desktop and I can see the Onedrive folder in Windows Explorer. However it’s just a folder on my local drive rather than a mounted remote drive – so when I attempt to copy into the Onedrive folder I am told there’s not enough space – and there isn’t – I have only 100GB locally.

How can I upload a large data set to onedrive without having to cache on local machine in the Onedrive sync folder? I tried via the web upload but nothing seems to happen – I suspect is too large for uploading over the web.