Backup Methods: Pros and Cons
Three Types of Backup
Let's cover the options. We'll start with the three main types of backup, file based, image based, and virtualization, each with its own purpose.
File Backup
A file-level backup simply copies each file as it is on disk. If the file is updated, it is found and backed up. This approach works well for only backing up specific folders. Often online backup services use file based backups. This approach can also back up different sets of files on different schedules.
Restoring means copying those files back into their original place. If downloading over the Internet, it might take a while to download a large amount of data.
File based backups do not back up operating systems, so in case of a disaster one would need to install and configure an OS like Windows, then restore files, and reinstall any applications and install any security updates. In other words, a full recovery of a dead server or PC is a very manual process.
File level backups tend to be fast and use less storage because only changed files need to be saved. They work well if the PC is disposable, and the files can be easily restored.
Image/Full Disk Backup
An image, or bare metal, backup process looks at the underlying disk and backs up an entire disk or partition at once. For incremental backups, it finds any sectors (bits of files) that have changed. The image can be mounted as a disk, to facilitate restoring only some files, or it can be written onto a new disk. This allows fast restores in case of disk failure, or even to different hardware, such as the loaner PC we provide with ITS TeamCare.
Image backups "take a snapshot" of a disk. Just like it sounds, the snapshot is a point in time image. In case of problems, it is very fast to revert to a previous snapshot. Many image based backup work this way...they take a snapshot, to get a consistent disk, back up the snapshot, then release it.
Restoring an image based backup to an empty disk recovers everything...the operating system, programs, settings, and data files. This makes it the best choice over file-level backups for critical servers and PCs, or any device that will take a long time to recreate/configure.
Image backups typically either keep a rolling copy (each day, combine the oldest two images, to retain 30 days of backup) or keep multiple copies (e.g. 8 weeks of backups with one full backup every other week). Typically off-site copies can simply be carried to a different location.
Virtualization/Appliance
The lowest-downtime backup solution typically uses an appliance to store image backups, but then it can simply boot up the source computer in a virtual environment inside the appliance. A company might back up a critical server every 15 minutes. In case of a server failure it can immediately "spin up" that server as a virtual server, letting staff get back to work within minutes, and minimal data loss.
Restoring an image based backup from this appliance or service to an empty disk recovers everything...OS, programs, and data files.
Often these appliances keep a rolling backup and also keep points in time, for example hourly for 48 hours, daily for the last 7 days, weekly for 4 weeks, and then monthly backups, typically either for one year or all time.
This option tends to be more expensive, both because it requires a decently powerful appliance and also because typically the backups are uploaded to a cloud service for long term and off-site storage. The trade-off is the limited downtime for staff, compared to obtaining new hardware and restoring from backup.
Backup Strategies
You may have heard of the "3-2-1" strategy. One must keep at least 3 copies of data, on at least two different storage media, and keep at least one copy off-site. The off-site copy guards against fire, flood, tornado, and even a ransomware-infected network. Hackers will, after all, encrypt the backups first, making the off-site copy the last line of defense.
While rotating backups off-site, an organization might choose to keep extra copies. In a generational, or grandfather-father-son, backup, an extra copy can be kept. For instance, a monthly copy can be kept, in addition to weekly and daily backups. If rotating off-site disks, simply use three or more, alternating between two and occasionally rotating in the third disk.
March 2025
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