What is: Backups – a Review of Basic Concepts

Target Audience

This article is aimed at a non-technical audience looking for an introduction to or review of data backup options.
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Introduction

It’s a fact of life that computer files can be lost through human error or hardware crashes. A data backup is a process that duplicates a computer’s data files, creating copies that can be used if the originals are lost or damaged. Regular backups have been a necessary and standard part of professional computer operations for many years.
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Devices and Media

A backup process copies files, placing the duplicates on a separate storage device. The type of device you use can depend on cost, convenience, and the amount of data involved.

• Tape Cartridge — A palm-sized mechanism containing a spool of magnetic tape
  • Benefits: Relatively low media cost, portable, easy to store, fast backup speed, high capacity, reusable
  • Drawbacks: Expensive drive cost, tape is less common than other media
• Hard Drive — A standard computer hard disk drive, internal or external
  • Benefits: Speedy backups, low cost per byte, high capacity, unlimited reuse of media
  • Drawbacks: less portable than other media.
• Optical Disc — Blank CD, DVD, or Blu-ray media
  • Benefits: Low-cost drive and media, widely available, compact, easy to store, portable
  • Drawbacks: Limited or no reuse of media, backups can be slow
• Flash Drive — Solid-state data storage, such as a USB stick or solid-state drive (SSD)
  • Benefits: Fast backups, portable, rugged, reusable media, no moving parts to wear out
  • Drawbacks: Relatively high cost per byte compared to other media, although flash memory price has declined with advances in technology

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Types of Backups

Full Backups

As the name suggests, a full backup copies virtually every file on a computer. Although essential, full backups can be time-consuming and use large amounts of data storage space. It’s common to do a full backup once a month or once a week, with partial backups filling out the rest of the schedule.
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Partial Backups

A partial backup stores only a selection of files, so it is typically faster than a full backup and uses less space on the backup media.
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Differential Backups

A differential backup is a partial backup that copies only files changed since the last full backup. For example, a computer has 1,000 files. On the day after the full backup, 30 files have data changes, so a differential backup copies only those 30 files. The next day, 5 other files have changed. The subsequent differential backup copies 35 files — the ones from the first day plus those that changed on the second. With each passing day, more files might change, so backups can take longer and consume more data storage space.
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Incremental Backups

An incremental backup is another type of partial backup that copies files that have changed since the last backup of any sort, full or partial. Following the previous example, an incremental backup copies 30 files on the first day but only 5 on the second. Because it looks only for files that changed that day, an incremental backup typically takes less time and storage space than a differential backup. On the other hand, differential backups are easier to manage when you need to recover files after a hardware failure; the full backup and the most recent differential backup have all the files necessary, whereas every daily incremental backup is needed to rebuild your files.
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Piecemeal Backups

You can back up individual documents manually to an external drive, such as a USB flash drive. Although this is a simple backup option, it does rely on your ability to remember to perform the backup and increases the opportunity for human error to negatively affect your data.
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Handling Backup Data

Encrypted Backups

With most backup software you can choose to encrypt files, making the copies unreadable without the correct password. This feature can be important for backing up proprietary and confidential information, helping to keep it safe from hackers and identity thieves.
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Compressed Backups

Your computer may have large files or large groups of files. The more data you have to back up, the more you’ll spend on media. A technique called compression makes data more compact, squeezing the same information into fewer bytes of data and helping to save backup storage space and reign in media costs. Compression gives best results on general documents such as PDFs and spreadsheets; some types of files, such as JPEGs and MP3 sound recordings, are already compressed, making backup compression less effective on them.
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Deduplication

Another technique, called deduplication, is similar to compression in that it reduces the storage space needed for backups. The process looks for duplicate information in your original files and skips it during backups, storing a small piece of data instead that marks the location of the duplicate information. For example, a shared drive has folders belonging to hundreds of users, each of which has a copy of the company phone directory. Deduplication stores one copy of the directory and records the duplicate locations but does not store the duplicate files. When restoring files, the deduplication software recreates the data, duplicates included. Deduplication can be very effective at reducing backup media requirements.
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Database Backups

A database management system (DBMS) might require its own backup process in addition to the regular file backups on your computer; this is true in particular for commercial DBMSs such as Oracle and Microsoft SQL Server. An improper database backup can leave you without critical business records after a hard disk failure. Check with the database software’s documentation on backups for special requirements.
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Offsite Storage

An offsite backup involves storing backup media at a different geographical location from the originals. You can, for example, keep a flash drive containing critical file backups in a safe deposit box or other secure facility. Offsite backups preserve valuable information in case of flood, fire, or other calamity.
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Internet Backup Services

The growth of high-speed Internet access in recent years has made online backups possible. Services such as Carbonite, OpenDrive, and Barracuda offer automatic backups over the Internet. However, for home and small-office use, bandwidth and data caps may affect how practical this sort of service is. Even a single PC can hold terabytes of data, and a full backup that size could potentially take months. On the other hand, medium to large companies typically have much faster Internet service, making large online backups more realistic. Another important issue common to Internet backup services is that they cap the amount of data you can send them on a given day regardless of your Internet speed.
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Restoring Files

A restore operation works like a backup but in reverse; it copies files from the backup media to your main computer hard drive. A catastrophic failure may require a full restore of data, which can be an ordeal as you copy all of your data from your backup to your computer. To take another example, if delete a file accidentally, you might restore only that file.
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Conclusion

Backups serve as a critical “safety net” for your data, protecting it from crises ranging from fire and flood to computer viruses and hardware crashes. Backup hardware and software packages are available to suit any size business, whether you need a simple program for a one-person shop or a sophisticated solution for a global enterprise.

 

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