On Thu, 30 Jan 2020 at 07:36, Paul Smith <phhs80@gmail.com> wrote:
Dear All,

My new computer has got 2 disks: a SSD and a HDD one.

The SSD disk is large enough to have Fedora and my entire home
directory on that.

Now, I am intending to use the HDD disk for backuping. And my question
is: How should I format the HDD disk?

Assuming you know how to partition and format a disk, you need to think
about the filesystem type, partitions, etc. for the HDD.   

Using an internal disk for backups is no replacement for
external storage (cloud or removable drive) that is stored offsite.  
Internal backups can be useful when files are accidentally deleted,
the root filesystem is corrupted, or a system fails to boot.   You may
want to consider putting a stripped-down OS on the HDD for use
in repairing problems with the system on the SSD.   There are 
a number of suitable backup tools for this use case.  Fedora has:

$ dnf info timeshift
Copr repo for qgis owned by dani                                                                       8.1 kB/s | 3.6 kB     00:00
Fedora Modular 31 - x86_64                                                                              27 kB/s |  16 kB     00:00
Fedora Modular 31 - x86_64 - Updates                                                                    91 kB/s |  16 kB     00:00
Fedora 31 - x86_64 - Updates                                                                            41 kB/s |  16 kB     00:00
Fedora 31 - x86_64 - Updates                                                                           1.1 MB/s | 2.3 MB     00:02
Installed Packages
Name         : timeshift
Version      : 19.01
Release      : 1.fc31
Architecture : x86_64
Size         : 3.1 M
Source       : timeshift-19.01-1.fc31.src.rpm
Repository   : @System
From repo    : fedora
Summary      : System restore tool for Linux
URL          : https://github.com/teejee2008/timeshift
License      : GPLv3+ or LGPLv3+
Description  : Timeshift for Linux is an application that provides functionality similar to
             : the System Restore feature in Windows and the Time Machine tool in Mac OS.
             : Timeshift protects your system by taking incremental snapshots of the file
             : system at regular intervals. These snapshots can be restored at a later date
             : to undo all changes to the system.
             :
             : In RSYNC mode, snapshots are taken using rsync and hard-links. Common files
             : are shared between snapshots which saves disk space. Each snapshot is a full
             : system backup that can be browsed with a file manager.
             :
             : In BTRFS mode, snapshots are taken using the in-built features of the BTRFS
             : filesystem. BTRFS snapshots are supported only on BTRFS systems having an
             : Ubuntu-type subvolume layout (with @ and @home subvolumes).

This requires a filesystem that supports hard-links. Another approach is to create archives of 
the system as large files on an NTFS filesystem.   This can be useful if you have an
external case and a second system running MacOS or Windows.  Some people have 
multiple HDD's and periodically swap them with the old versions stored offsite.

--
George N. White III