Learn: backup basics, explained
Plain explanations of the questions people ask about backup: how many copies to keep and for how long, how backup types differ, how much data you can lose and how fast you must be back, how to protect backups from an attacker, how backup relates to an archive and to the GDPR, how long businesses in Germany keep email and what a procedural documentation covers, which storage to choose, and what Microsoft 365 does and does not keep. Each article starts with a short answer, cites a primary source for every outside fact and ends with an honest box on what Restow does today and what it does not do yet.
By Lucas Flores, IT Systeme Flores UG. Last updated
Which articles are there?
- The 3-2-1 backup rule and 3-2-1-1-0, explained Three copies, two kinds of storage, one location apart, and the extension with an immutable copy and zero errors. With a worked Microsoft 365 example.
- Does Microsoft 365 back up your data? What Microsoft keeps, for how long (recycle bins, version history, retention), why retention is not a backup, and what Microsoft 365 Backup is.
- Grandfather-father-son (GFS) backup rotation, explained Daily, weekly, monthly and yearly restore points with a calendar example, how it differs from keeping every backup for N days, and how it maps from tape to disk and object storage.
- Full, incremental, differential and synthetic full backups compared A comparison table for storage use, backup time, restore effort and chain risk, plus forever-incremental, changed block tracking and deduplication.
- Backup vs. archive: what each is for, and why one does not replace the other Recovery against retention, a comparison table, archiving vs journaling, why a rotating backup is not a record, the GoBD angle for German businesses, and how to run both.
- Email retention periods in Germany: 6, 8 or 10 years Which emails are commercial letters (6 years), accounting vouchers (8 years) or books (10 years), when the period starts, when you may delete, and what the GDPR adds. Not legal advice.
- Procedural documentation for email archiving under the GoBD: contents, structure and a template What the GoBD ask of a procedural documentation (Rz. 151 to 155), its usual parts, what an email archive needs in it, and a template to download. Not legal advice.
- RPO and RTO explained: how much data you can lose and how fast you must be back The two recovery objectives as NIST and SNIA define them, how backup frequency and restore paths set them, a worked example and a small calculator.
- Immutable backups, WORM, air gaps and ransomware: what protects a backup from an attacker How attackers go after backups, what Object Lock in governance and compliance mode does, what an offline copy adds, and what none of it covers.
- GDPR and backups: erasure requests, encryption and processors What Article 17 asks of a backup, what the EDPB and German authorities say, why backups usually expire, and where locks and holds collide with an erasure request. Not legal advice.
- Choosing backup storage: local disk, NAS, S3-compatible storage, tape and cloud compared Local disk, NAS and NFS, S3-compatible object storage, tape and cloud archive tiers compared on cost, durability, immutability and restore speed.
- Backup glossary reference Short definitions of backup, restore and retention terms, from 3-2-1 rule to WORM, with links to the articles and features pages that go deeper.
How are these pages written?
They are evergreen: they explain the idea first and the product second. Numbers either come from a cited source or are labelled as examples, and each page shows the date it was last checked. Where a page says what Restow does, it is limited to what the released version does; planned work is called planned.
Where do I find the product facts?
The features pages state what Restow does today, the roadmap what is planned, and the blog goes into pricing, lock-in, restore testing and GoBD.