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External hard drives
External hard drives are fast backup devices, meaning that full backups of large amounts of data can be performed on a daily schedule.
However, hard drives generally have no support for encryption and storing previous versions are cumbersome.
Hard drives require you to manually take data offsite, they don't keep previous versions and are generally not encrypted. However, they are one of the cheapest backup solutions.
Tape Backup
Tape backup is a very popular medium for backing up larger amounts of data.
Functioning very similar to audio cassette tape drives, a tape data backup drive stores data by encoding it magnetically onto the tape.
Sequential access
Unlike hard-drives, tapes can only be read and written sequentially, meaning they need to fast-forward/rewind to seek to the appropriate position on the tape.
For example, if a file needed to be recovered from a tape, the tape drive would need to wind the tape to exactly the correct position and read the magnetic code from the ribbon to retrieve the file.
Drawbacks of tape-based backup
- Tape suffers from slow seek performance due to its sequential nature. Hard drives and solid-state drives offer better performance as they can seek randomly.
- The constant physical fast-forward/rewinding nature of tape backup can cause what's known as a "shoe-shining effect". This causes transfer speeds to suffer, as the tape drive must slow down to read the same amount of data and eventually will wear the tape out and cause data to be unreadable.
- Tapes are very sensitive to heat. This becomes
a major problem when tapes are often stored in fire-proof safes.
During a fire the tape may not be destroyed, however when it comes to recover from the tape, the recovery operation fails due to the magnetic encoding being eroded from the extreme heat in the fire.
Data backup tapes have a maximum non-operating temperature of 66C exceeding these limits will render the backup data useless.
- Tape requires tape-transport and fossil-fuels to take offsite.
Network/direct attached storage
Network and disk attached storage are more expensive solutions.
These solutions are more robust than external hard drives as they ensure the data is backed up to another machine across the network.
NAS/DAS solutions are generally not encrypted, nor are they designed to operate over a slow internet link, so this means a fast network is required to allow the backup to complete in a reasonable time.
NAS backup solutions are not designed for offsite backup, so the user still needs to manually transport data away from the primary storage location.
Writeable/re-writeable optical media
Optical media has been around since the 1980's and was a quantum leap in storage capacity when the CD was first released.
Optical media can be great for archiving due to its inherent WORM (write once read many) design, however it's difficult to use as a primary backup for regularly updated information.
Optical media is best suited for archival purposes, however the limited data capacity of optical media could be an issue for massive data archiving.
