Any way to take backup in single file

In there any way to take backup on every day in single file from 3 node cluster and letter i can restore same on cluster.
Because as we checked from COPY FROM/TO command multiple back up files are created on their local disk.

Is it problematic, that there are multiple files? You can import multiple files at once with COPY FROM or import a whole folder.

For Backups in general you should probably rather use Snapshots though:

And manage the backups through CrateDB