@Cragdoo 

no I use robocopy
robocopy e:\ f:\ /B /SECFIX /COPYALL /MIR /R:1 /W:5 /LOG:c:\log2.txt /TEE

    /B : backup mode for copying files to which the account you are operating with does not have access
    /SECFIX : fixes the security settings of what is being copied 
    /COPYALL : copies everything (data, attributes, time stamps, NTFS ACL, owner, audit)
    /MIR : copies the directory structure
    /R : retry number
    /W : seconds of waiting time before each retry
    /LOG : log file
    /TEE : displays on screen over chand write to the logand write to the log

should have added this is to copy files from VCC-B repo , so robocopy not an option

I used to, before the NAS engine. The original engine from FastSCP could so good at those tasks. Better than Robocooy or Terracopy from my experience 10-14 years ago.

I don’t think it reconnects, but I could be wrong. 

As far as 300TB, could you break it up into smaller chunks? That is going to take a super long time. 

What is your target? on prem SAN?

If all your data is stored on a VM why not an instant vmdk recovery to the target VM then storage vmotion?

I was thinking this also, but then realized he wanted to use file explorer, so maybe he doesn’t want the whole VM, or to skip the VMware portion of things. 

Yeah, copying anything at the moment with VCC for tenants and moving repos around has been a sore spot for MSPs (us included).  I would rather use the script from support that starts the process to move the main files and then another utility like Robocopy to move the actual data over and then finalize the script.  To me this is the safest bet overall.

so to give more info

customer, uses VCC-B for off-site backups, but wan’t to move that backup data into Google Cloud …..