You say that data is critical for your business, have you considered a cloud backup as well? AWS has very cheap storage options depending on the speed the file needs to be available at. Also I’d definitely not go with flash memory, bit flips can be a real danger. I’d go with a 1 TB HDD in an enclosure, additionally to a cloud backup
https://aws.amazon.com/s3/pricing/?p=pm&c=s3&z=4
This was what I was thinking about. I would definitely not use gdrive a a critical backup and the glacier tier at aws should be sufficient and cheaper than a hdd for years