Is it a good idea to transfer files from google drive to external hard drive as a backup? 

If you are doing this to keep a copy of all your files on Google Drive, consider a more secure and durable option like Vaultastic.

Backing up google drive to an external hard drive increases data loss, corruption, fragmentation, and tampering risks, making the solution very risky.

Vaultastic’s cloud-based data archiving solution provides an excellent alternative to back up OneDrive files and reduces risks related to accidental or intentional erasures.

Vaultastic complies with industry regulatory norms and provides exceptionally durable storage to put you at ease.