External Hard Drives, Backup and Data Recovery
External hard drives are very popular because they offer flexibility and capacity for low price. External hard drive is one ore more hard drives mounted in an enclosure. This enclosure contains power supply and one of standard interfaces, usually USB. In other words, external hard drive contains a minimum set of components to connect a hard drive to the computer.
The main advantage of external drives is portability. With external drives it is very simple to transfer files from one place to another. Additional flexibility is in the universal enclosure. You can connect any standard drive with supported disk interface (ATA/IDE, SATA or SCSI). This way you can simply remove hard drive from any computer and put it into a suitable enclosure. This disk can now be connected to any computer without accessing motherboard or internal cables. Drives supporting SCSI, SAS, FibreChannel or eSATA can be connected directly to the hard drive controller, while other types need interface electronics which usually provides USB or LAN connection. External drives with LAN connectivity are usually used as NAS—Network Attached Storage.
External drives need to be formatted before they can be used. In fact, everything that applies to internal drives applies also to external devices. If portability is your goal them make sure you will use file system that is supported at all computers. NTFS in mainly used in Windows environments, MACs use HFS, while Linux users usually choose ext3. FAT32 is one of the simplest compromises. It is supported by all operating systems but it is limited to only 4 GB. To be disk size independent you need to choose one of primary file systems and if necessary add support for it on other computers.
External Hard Drive For Backup
External hard drive is an elegant and cheap storage for backups. You can manually (or better with dedicated backup software) copy all the files that need to be saved to this drive. After the copying is finished store the drive in a safe place. This kind of backup is convenient because the backup process is simple and quick and the same applies also to the restoration process. All the files are available anytime at any place.
However, external hard drive is still hard drive. It can fail. You should never rely on this drive as a 100% backup. This is just another disk with your files. It is very unlikely that both, your main computer and the external drive will fail at the same time but this possibility has to be taken into account. For the highest security you should have backups on different media stored at different locations.
External Hard Drive and Data Recovery
Data recovery from external drives is practically the same as for internal hard drives. Any data recovery software can be used to recover deleted files or corrupted file system. Many undelete problems can be solved via USB connection. But for greater flexibility it is advisable to connect the disk directly to the computer (without USB interface). This will enable the recovery software to communicate with the hard drive at the lowest level.
External hard drive enclosures can also be used for data recovery where the corrupted disk can not be directly connected to the computer. For example, if you have a SATA disk and computer which only supports ATA/IDE disks you can connect it with external enclosure with SATA/USB interface.