You’re getting your terminology confused.
Internet download speeds are measured in Gbps (lower case b), which means Gigabit per second.
HDD & SSD Read/Write speeds are measured in GB/s (Upper case B) means Gigabyte per second.
900 Gbps is equal to 112.50GB/s. 1,000 Gbps is equal to 125GB/s.
I don’t know the model of your hard drive but I’m pretty sure there wouldn’t be any bottleneck issues.