Sources and destinations
The source answers what must be protected. The destination answers which failures the backup can survive. A perfect folder selection on unsuitable storage is still a weak backup, so treat both choices as equally important.
Choosing sources​
Select the folders containing irreplaceable work, photos, projects, and other personal data. The content tiles show estimated sizes and file counts before the first run. These estimates help you understand both the first-run duration and the minimum destination capacity.
Good sources are data you created or collected. Windows and installed applications can usually be reinstalled; their program folders are not a substitute for a system image and may contain files that cannot be restored into a working installation by simple copying.
O&O AutoBackup normally excludes operating-system and program folders because they are not useful in a file-only recovery. Custom exclusions and file-type groups can be managed in Settings → Folders and Settings → Filter.
Cloud placeholders require special care. When OneDrive integration is enabled, an online-only file may have to be downloaded before it can be backed up. This uses bandwidth and temporary local disk space. O&O AutoBackup can return the file to its placeholder state after processing. See Protect OneDrive with an offline backup.
Choosing a destination​
The destination page displays available capacity and how much the backup is expected to use. O&O AutoBackup creates its own folder; other data on the disk remains untouched.
- USB drive: portable and easy to disconnect from ransomware, but protect it from loss and damage.
- Separate internal disk: always available and fast, but still inside the same PC.
- Network share: useful for several PCs; confirm that the signed-in account has persistent access.
- WebDAV or S3: suitable for a compatible remote service; performance depends on connection speed and provider behavior.
What each destination protects against​
| Destination | Survives source-disk failure | Can be isolated from the PC | Available without internet | Main concern |
|---|---|---|---|---|
| Another folder on the same disk | No | No | Yes | Same hardware and malware boundary |
| Separate internal disk | Yes | Usually no | Yes | Remains exposed inside the PC |
| Removable USB drive | Yes | Yes, when disconnected | Yes | Must be connected regularly and stored safely |
| NAS/network share | Yes | Depends on permissions/snapshots | Usually on local network | Credentials, network, and ransomware reachability |
| WebDAV/S3 | Yes | Depends on account design | No | Provider, credentials, bandwidth, and recovery time |
For important data, one destination rarely covers every risk. A regularly connected destination gives frequent recovery points; a disconnected or separately credentialed copy provides isolation.
Removable-drive safety​
Windows can assign a different drive letter after reconnecting a device. O&O AutoBackup records the destination volume and can relocate it safely. It refuses to write to an unrelated disk merely because that disk received the old letter.
This is why you should use Choose another destination when replacing a drive instead of making a new device imitate the old path. O&O AutoBackup can then record the intentional change.
Destination space​
If space runs low, reduce how long old versions are kept or free space on the destination. With managed retention, the oldest eligible versions are removed while the newest version of every file is preserved.
Capacity planning should include change, not only today's source size. A 500 GB photo archive that rarely changes needs little extra version space; a 50 GB project whose large files change daily can create far more history. Check the destination after the first week and again after a typical busy period.
A permanently connected backup can be reached by malware or accidental deletion. Periodically disconnect a removable destination or maintain another independent copy.