When I used to hear the term “backup,” it didn’t occur to me that it could ever mean more than simply backing everything up. And I didn’t think about why that was necessary. But, as I mentioned in my post last month, “When a Disaster Isn’t an Act of God,” “the reality of it [backup] can be complex.” What’s more, backup is only part of a greater process—recovering from a disaster, known as disaster recovery, which requires both backing up data and then restoring it, whether that’s one file for one user or all the data for an entire company.
The complexity of backup is my topic today—not the complexity of doing a backup or restoring data, but the complexity of the sheer number of available types of backup and the options for where data can be backed up.
There are several types of traditional backups. The most common are listed in the following table:
|Type of Backup||What Is Backed Up||Pros||Cons|
|Full backup||Everything the admin opts to back up, which might include operating systems, data files, and configuration files||Restores are fast and easy given that everything is backed up to, and therefore retrievable from, one place||Depending on the amount of data backed up, a full backup can consume a lot of time and storage space; each full backup is typically saved rather than overwritten by the newest full backup|
|Differential backup||Everything that has changed or is new since the last full backup||Faster to complete and consumes less storage space than a full backup because files are not duplicated unless they’ve been modified since the last full backup||Restores can be slower and more difficult than from a full backup but are faster than from an incremental backup|
|Incremental backup||Everything that has changed or is new since the last incremental backup||Faster than a full backup; consumes less storage space than full or differential backups||Restores can be slower and more difficult than for full or differential backups|
|Synthetic full backup||Everything, but synthetically: uses incremental backups and an existing full backup to automatically replicate a full backup without actually doing a full backup||Automatically provides a backup equivalent to a full backup without the needed time to run one; restores are as fast and easy as they are from true full backups||Consumes as much storage space as a full backup|
|Incremental-forever backup||Everything that has changed or is new since the last incremental backup||The same as an incremental backup except that the backup server automates restores so that the admin or IT team doesn’t have to combine and restore backups manually|
|Mirror backup||Everything the admin opts to back up, which might include operating systems, data files, and configuration files||Uses less storage space because only a single copy of the last mirror backup is kept||Can result in lost data|
Other terms you might hear in relation to backups are “snapshot” and “flat backup.” Neither is considered a true backup in the traditional sense, but rather as alternatives to traditional backup methods.
A snapshot, according to TechTarget, is “a set of reference markers, or pointers, to data stored on a disk drive, on a tape, or in a storage area network (SAN).”[i] A ComputerWeekly.com article alternatively describes snapshots as “point-in-time copies of your data.”[ii] They can be looked at as virtual copies of data. Snapshots don’t necessarily negate the need for an actual backup, but can make restores much faster and easier and can be a valuable part of a backup plan. There are almost as many types of snapshots are there are types of backups.
Flat backups use snapshots without also using traditional backup software. Essentially, snapshots are made and copied. The original snapshots and copies are then stored in different locations. If the original snapshots are lost, the copies can then be used for a restore. Flat backups require little storage space and can make backup faster and easier.
Where to Back Up Systems or Data
In addition to different types of backups, different backup locations can be used for any type of backup discussed previously.
|Local backup||The storage source is located close to, even within the same facility, as the data being backed up||Accessing files for a restore can be faster and more convenient than from a different location; costs involve only the medium used and man hours||In a disaster, having backups at the same facility as the original data can increase risk and hinder restores; can require significant hardware|
|Offsite backup||The storage media is located in a different facility from the data being backed up||Facilitates restores when the facility that data is located in is damaged||Might increase costs|
|Online backup/cloud backup||A form of offsite backup where data is backed up to a remote location, typically a commercial data center, using an Internet connection||Pretty much always available; can offload IT and compliance management needs from the organization itself; might include data replication for added protection; can be virtually automatic once set up||Might increase costs; restores can take longer; a high-speed connection is needed|
|Hybrid cloud backup||Combines a local backup and a cloud backup; the local backup is typically used for a restore and the cloud backup available should the disaster affect the facility where the local backup resides; often involves the use of an appliance||Offers added protection with the convenience and speed of a local backup||Appliances must be purchased, managed, and maintained|
|Instant VM recovery||Used exclusively for virtual machines (VMs) to restore VMs by running them virtually from a backup file||Can facilitate a rapid restore for virtual environments||Not automatic; must be initiated by an admin|
|Remote backup||A form of offsite backup that might be used interchangeably with online or cloud backup||Same as offsite and online backups||Same as offsite and online backups|
|FTP backup||A remote backup where data is backed up to an FTP server over an Internet connection||Same as offsite and online backups||Same as offsite and online backups|
Additional Backup Considerations
Which storage medium you use and how often you run a backup are additional considerations that further add to the complexity of backups and restores. Storage mediums can include tape, hard disk drives (HHDs), solid-state drives (SSDs), and flash. How often you should backup is largely dependent on the criticality of your data and how often it changes.
If you’re not an IT admin, many of whom already know all about backups, I hope this information gives you a taste of what your IT admin has to know and keep up with. Multiple online resources are available that delve deeper into backup and restore if you’re interested.
[i] TechTarget. “Data backup types explained: full, incremental, differential and incremental-forever backup.” July 2010. http://searchdatabackup.techtarget.com/tip/Data-backup-types-explained-Full-incremental-differential-and-incremental-forever-backup.
[ii] ComputerWeekly.com. “Snapshot technology: The role of snapshots in today’s backup environments.” January 2011. http://www.computerweekly.com/tutorial/Snapshot-technology-The-role-of-snapshots-in-todays-backup-environments.