Backup vs sync: why you probably need both
Two different jobs people confuse
Sync services keep the same files identical across your devices in real time. That is wonderful for working across a laptop and a phone, but it has a dangerous property: if you delete a file, or a piece of malware encrypts it, sync faithfully propagates that change everywhere. The bad version is now your only version.
Backup does a different job: it keeps separate, historical copies you can roll back to. The defining feature is versioning — the ability to recover the file as it was last week, before the mistake. If a service cannot take you back in time, it is storage, not backup.
A recovery plan you can actually trust
A widely used rule of thumb is to keep three copies of anything important, on two different kinds of media, with one copy off-site. Cloud backup naturally provides the off-site copy; a local drive covers the fast restores. The two together mean no single failure — theft, drive death, or a bad sync — takes everything.
The step almost everyone skips is testing the restore. A backup you have never restored from is a hope, not a plan. Once, deliberately recover a file from your backup and confirm it opens. Discovering a broken backup during a real emergency is the worst possible time.