In any case, whether you make a full backup of PC or only user data backup,
the most important thing is choosing of a backup device.
There are several criteria for evaluation of available solutions:
capacity, transfer speed, durability and cost per gigabyte.
External hard disk has the best performance and enough capacity for
huge data amount. It is no problem to store several backup archives,
which can be useful to restore after virus damage or hardware fail.
Because data files can be opened, but it contain distorted or wrong information.
Such damaged files backing up without any problem and backup software
does not detect any error. But user cannot read it by associated software
or get distorted data.
High transfer rate allows to do full and everyday backup with
very short time period. It is the best solution for always-in-use servers.
Data backup can be done outside of working hours
and users do not wait when backup finished.
External hard disk is a fragile device. It is very sensitive for shaking.
But cheap price per gigabyte and large amount of overwrite cycles
make hard disk is very popular backup device.
DVD discs durable to shaking, electrical and magnetic fields.
It reliable solution for offsite backup, which prevent data loss after
nature or technological disaster. DVD discs must be kept
in safe room with limited access. Strong encryption may also
help to protect private and corporate data against unauthorized access.
DVD-RW disc has limited amount of rewrite cycles and must be
replaced before it exceeded. Famous manufacturer declare this operational characteristic.
Also each backup archive must be tested to integrity.
DVD-RW discs several time slower in comparison with hard disks,
but it is portable and compatible with wide range of computers.
USB flash disks durable to shaking, but sensitive to electrical fields.
Also connection/disconnection to PC can damage content or disk.
But light weight and small geometrical size make it the best backup device
for mobile computers.
Transfer performance can be vary and depends on model and manufacturer.
One flash disk with the same capacity may be several time faster than another model
even from the same manufacturer. Amount of overwrite cycles is large,
but it also depends on model.
Media cards are the same as usb flash disks,
but it requires special card reader drive. There are a lot of cards on the market today:
MultiMedia Card (MMC), Memory Stick (MS), CompactFlash (CF), Secure Digital (SD).
They used to data transfer between digital mobile devices:
laptop, netbook, photo camera, music and video player, smartphone.
Desktop computer may require additional drive to read these cards.
Media cards more expensive than usb flash device with the same speed and capacity.