If you have properly mounted your hard drive (if on Linux, using static mount via /etc/fstab), then your Node should start up again automatically after your machine has rebooted.
However, power failures on machines not protected by a UPS or other abrupt disconnections may cause database corruption leading to errors such as:
database error: database disk image is malformed or
database: file is not a database in your logs).
Incorrect mounting could lead the Node to not recognize the proper data location where the Node was previously storing the data, resulting in node crash.
In case of using the storagenode docker version, it will continuously restarted until the Node Operator would fix the problem.
In case of using the Windows GUI, the service will not restart automatically and the Node Operator should fix the problem and restart the service.
Such failures should be attended to immediately as they can lead to the node getting disqualified.
Here are instructions on how to fix a malformed database disk image. If the database is not recognized ("file is not a database"), recovery of this database will be impossible, and you will need to recreate it.
If you need assistance, please ask on our forum.