HDD Backup

Backup to external HDDs

A big advantage of external hard drives is that they can be stored separately from the original data. Doing so offers protection against theft, fire or water accidents that might destroy your original data.

External HDDs are a good choice as a backup medium, because they have high capacities are easy to handle and prices are affordable even for terabytes of space.

Advantages of external hard drives

Capacity: Hard discs offer a huge amount of space. You can most likely store backups, even versioned backups, of all your data on one external HDD.

Compatibility: Current operating systems recognize external hard drives automatically and you can use them just like normal internal HDDs.

Writability: External hard drives can be re-written an unlimited amount of times.

Disadvantages of external hard drives

Transport: 3,5″ external hard drives need their own power supply. Also, they are the largest and heaviest backup mediums in comparison to DVDs, tapes etc.

Durability: Hard discs consist of a rotating cylinder on which data is stored magnetically and accessed by a moving read/write head. Shock and improper handling can lead to defect and thus data loss.

Factors for a fast Backup

Apart from the speed of your computer the speed of the external hard drive and the used connection type play the most important role in backup performance.

Pairing a fast external hard drive with a slow connection interface will seriously decrease the data transfer rate. When purchasing hard drives you should look for the read and write speed of the drive themselves as well as the data transfer rate of the connection type.

Backup to external USB Hard Drives

2,5″ USB hard drives are available with capacities of several TeraBytes. They usually have a slower rotation speed than their 3.5″ counterparts – but they are robust,  unobtrusive and lightweight.

For easy use, the power connection should be integrated in the USB connection. This feature is supported by most 2.5”/1.8” drives. These discs are also plug & play compatible, which means that you can just plug them in and out of the computer without restarting.

For large data sets, the maximum data throughput plays an important role:

USB 5 Gbit/sUSB 10 Gbit/sUSB 20 Gbit/sUSB 40 Gbit/s
USB 3.0
USB 3.1 Gen 1 USB 3.1 Gen 2
USB 3.2 Gen 1 USB 3.2 Gen 2 USB 3.2 Gen 2x2
SuperSpeed USB 5Gbps SuperSpeed USB 10Gbps SuperSpeed USB 20Gbps
USB4 Gen 2x2 USB4 Gen 3x2

USB 3.xx Backup

It is advisable to use USB 3 for backups. Backups via USB 3 are considerably faster than via the previous USB 2 interface. Upgrading old computers that currently only support USB 2 with USB 3 chips is inexpensive and worthwhile. 


Data Security

It is risky to use the same USB hard disk for backups every day. Better are two or more devices which you can use in a round-robin fashion. This protects you against hardware faults and allows you to keep several versions of your files. Always take one of the drives back home or keep it separated from the others to protect yourself from theft or natural catastrophes (fire, water, over voltage).

Hard Drive Formatting

There are limits that come from the file system or the operating system. A file system is a kind of basic format/structure for a hard disk that is created when the medium is formatted and later filled with files. There are four common file systems that can be used for hard drives on Windows computers:


Partition Size

up to 2 GByte

Maximum File Size

2 GByte

Partition Size

512 MByte to 2 TByte

Maximum File Size

4 GByte

Partition Size

up to 512 TByte

Maximum File Size

only limited by the partition size

specifically for flash storage

Partition Size

up to Windows 10 v1703 – 256 TB
from Windows 10 v1709 – 8PB

Maximum File Size

up to Windows 7 – 16 TB

from Windows 8 – 256 TB
from Windows 10 v1709 – 8PB

FAT32 partitions are supported by most operating systems and are therefore widely used. It has some restrictions, for example a maximum file size which your backup archive might exceed, but Z-DBackup offers an automatical workaround and splits your backup file into multiple smaller portions if the size limit is reached (it creates a multi-spanning archive).