What is disk-based backup?

Disk backup is a type of secondary or tertiary storage used to recover data that is lost when primary storage fails. Disk backup uses disk drives that contain spinning disks and moving read/write heads. They use optical or magnetic media to record data. Disk drives are block storage devices that divide their capacity in to “blocks” using logical block addresses (LBAs). Disk drive interfaces include SCSI (Small Computer System Interface) and SAS (Serial Attached SCSI)for large server disks, and PATA (Parallel Advanced Technology Attachment) or SATA (Serial Advanced Technology Attachment) for desktop hard drives.

Disks tend to be more volatile and breakable than solid-state drives, but are less likely to leak data in long term backup and archival storage. Both tape and disks with magnetic mediums are vulnerable to magnetic wave damage. IT organizations commonly use disk-based or tape-based storage to backup primary storage. The main advantage of tape-based storage is cost. Large enterprises will sometimes prefer tape backup over disk backup because they have so much to store and they want to cut costs. However, disk-based storage is superior to tape storage in almost every other category.

Advantages Over Tape
Although disk requires some seeking motion to find data on the surface of the medium, tape often takes much longer to wind the material up to the desired data point. On tape, data must be recorded sequentially, causing many disadvantages, while disk can write data in a more organized and variable fashion for faster access. Disk’s ability to backup data and recover it so much faster than tape is worth the extra cost to many organizations. IT manufacturers have narrowed the data density and cost-per-bit gap between disk and tape.

Disk drives save organizations money in other ways. With a tape backup system, you have to pay a vendor to physically pick up tapes or host tape libraries remotely in order to have backup from a different location. For disk backups, it is easy to accept copies of data from a remote location with a server and SATA array. This requires less time and maintenance because remote backups are transferred much easier with disk.

If you are using data backup merely to protect against accidental deletion, disk is usually the best option. Disk backup systems can produce point-in-time snapshots faster and more frequently than tape. Tape also experiences an effect called shoe-shining at times. This happens when streaming falls below a certain transfer rate and a back and forth motion by the play-head causes the tape to degrade.