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How should you back up a physical server?
A physical server is backed up as a whole machine: system, applications, accounts and data, as a restorable image, supplemented by a backup of files and databases. Backing up only the data folder means that, on the day of the failure, everything has to be reinstalled before the files can be put back, which often takes several days.
Key points
- A system image (bare-metal) to restart, files and databases to restore a document or a table.
- An SQL database is backed up with a tool that understands the database, not by copying files while it is running.
- The copy must leave the server: a second internal disk survives neither fire nor ransomware.
- Plan the replacement hardware: RAID controller, licence tied to the serial number, dongle.
- Restore the image at least once a year on a test machine, and a file every quarter.
Two levels, both useful
The system image, or bare-metal backup. It captures the server’s disks. It is used when the server no longer boots, when the disk has died, or when ransomware has hit the system. Microsoft recommends this type of backup to rebuild a domain controller, in particular because it can be restored on different hardware. You still need to know which replacement hardware it will boot on: a very specific physical server (RAID controller, licence tied to the serial number, dongle) is hard to restore elsewhere. Planning for this before the failure is part of the backup.
Files and databases, in addition to the image. They are used to restore a document or a table without restoring the whole machine. An SQL database is backed up with a tool that understands the database (transaction consistency), not just by copying the files while the engine is writing. For SQL Server, Microsoft describes three recovery models: only the full recovery model, with frequent transaction log backups, lets you return to a precise point in time.
The image can be taken daily. The database backup can be hourly if data is entered continuously. The two histories do not need to have the same retention period.
| System image | Files and databases | |
|---|---|---|
| Used to | Restart a dead or infected server | Restore a document, a mailbox, a table |
| Usual frequency | Daily | Daily to hourly (database log) |
| Restoration | Equivalent hardware or virtual machine | To a folder or a test database |
| Point to watch | Drivers, RAID, hardware-bound licences | Transaction consistency |
What not to forget on a physical server
- The contents of the data disks and the configuration (shares, scheduled tasks, certificates, service accounts).
- Databases and business applications, with a consistent method.
- Email if it is still hosted on this server (on-premises Exchange), separate from Microsoft 365.
- A copy outside the server itself. Microsoft points this out for SQL Server: backups must be on a different physical device from the database files, not on another partition of the same disk. A second internal disk survives neither a burnt-out power supply nor encryption of the system.
- Installation media and software configuration: the ANSSI, France’s national cybersecurity agency, recommends documenting them, so that you can rebuild without searching.
- The backup encryption key, stored somewhere other than on this server.
- A test: restore the image at least once a year on a test machine, and a file every quarter. The method is in How to test that a backup works.
Typical recovery times
Without an image: reinstall the system, drivers and applications, then copy the files. For a business server, it often takes one to three days, provided the installers and licences can be found.
With an image and an off-site copy: the time depends on the volume to be brought back and on the replacement hardware. This is the RTO, to be measured, not guessed. NIST advises anticipating hardware replacement through agreements with suppliers. If this time remains unacceptable, the physical server needs a DRP: restarting on a standby instance from the backup, while the hardware is repaired.
If several servers must be restarted, the order matters. The ANSSI recommends setting a restoration order in advance that takes account of dependencies (directory, DNS, databases) and the criticality of applications.
At WeDoBack
WeDoBack backs up Windows and Linux physical servers, as well as SQL Server, Exchange and business software, and can restore the complete server, software and settings included, or just files. Data is encrypted on the machine before it is sent; the key stays with the client. The agent on a physical server is billed at €20 excl. VAT per month in the SMART public price list, in addition to storage at €49.99 excl. VAT per TB per month; with INTEGRAL, storage ranges from €100 to €65 excl. VAT per TB per month depending on volume, with agents included depending on the tier. An archived system image option is available: €15 excl. VAT per month for a half-yearly image, or €60 excl. VAT per month for a monthly image, per server and per TB. If the hardware cannot be replaced in time, the DRP restarts the servers on standby instances from the version you choose.
Frequently asked questions
Can a system image be restored on different hardware?
Often yes: Microsoft states, for example, that a Windows Server bare-metal backup can be restored on different hardware. In practice, storage drivers, RAID controllers and hardware-bound licences cause problems. You need to have tried it once, on a physical or virtual machine, before you need it.
Do you still need to back up a physical server if its disks are in RAID?
Yes. RAID lets you keep running when a disk dies. It also faithfully replicates a deletion, a corruption or ransomware encryption. It is not a backup: there is no history and no copy outside the server.
How often should a physical server be backed up?
The image can be daily. A database with continuous data entry may justify backing up its log every hour, or even more often: this is what lets you return to a precise point in time. The frequency follows from the acceptable data loss, the RPO.
Further reading
Sources
Documents consulted in October 2026.
- Information system backup – The fundamentals (ANSSI-BP-100, v1.1, 27 November 2025) — ANSSI, France’s national cybersecurity agency
- AD Forest Recovery – Backing up a full server — Microsoft Learn
- Back up and Restore of SQL Server Databases — Microsoft Learn
- SP 800-34 Rev. 1, Contingency Planning Guide for Federal Information Systems — NIST
- Offers and prices — WeDoBack
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