Backup is the keyword in case of data storage. Even the newest technologies deployed will not work out if one day turns out that some hard drives with crucial data don’t work, RAID may failed owing to the numbers of broken hard disks, your SAN has been destroyed or data have been accidentally (or not) permamently deleted. Then you will face towards the backup … if you have any of course.
What is the backup ?
The backup is nothing more then a copy of data which are being kept in case of any failure which lead to lost or corrupted data. Backups are performed for three primary purposes:
Disaster recovery addresses the requirement to restore all, or a large part of, an IT infrastructure in the event of a major disaster. The backup copies are used for restoring data at an alternate site when the primary site is destroyed due to a disaster. Based on recovery requirements, organizations use different backup strategies for disaster recovery.
Operational backup is a backup of data at a point-in-time (PIT) for the purpose of restoring data in the event of data loss or logical corruptions that may occur during routine processing. The majority of restore requests in an organization are classified in this category. An example of an operational backup is a backup taken just before a major change to a production system occurs. This ensures the availability of a clean copy of production data if the change corrupts the production data.
Backups are also performed to address long-term storage requirements. For example, an organization may require to keep transaction records and other business records required for regulatory compliance.
Types of a backup
Full backup: As the name points out, it is a full copy of the entire data set. Organizations typically use full backup on a periodic basis because it requires more storage space and also takes more time to back up. The full backup provides a faster data recovery.
Incremental backup: It copies the data that has changed since the last backup. For example, a full backup is created on Monday, and incremental backups are created for the rest of the week. Tuesday’s backup would only contain the data that has changed since Monday. Wednesday’s backup would only contain the data that has changed since Tuesday. The primary disadvantage to incremental backups is that they can be time-consuming to restore. Suppose an administrator wants to restore the backup from Wednesday. To do so, the administrator has to first restore Monday’s full backup. After that, the administrator has to restore Tuesday’s copy, followed by Wednesday’s.
Cumulative (differential) backup: It copies the data that has changed since the last full backup. Suppose for example the administrator wants to create a full backup on Monday and differential backups for the rest of the week. Tuesday’s backup would contain all of the data that has changed since Monday. It would therefore be identical to an incremental backup at this point. On Wednesday, however, the differential backup would backup any data that had changed since Monday (full backup). The advantage that differential backups have over incremental is shorter restore times. Restoring a differential backup never requires more than two copies.
Synthetic backup: Another way to implement full backup is synthetic backup. This method is used when the production volume resources cannot be exclusively reserved for a backup process for extended periods to perform a full backup. A synthetic backup takes data from an existing full backup and merges it with the data from any existing incrementals and cumulatives. This effectively results in a new full backup of the data. This backup is called synthetic because the backup is not created directly from production data. A synthetic full backup enables a full backup copy to be created offline without disrupting the I/O operation on the production volume. This also releases network resources from the backup process, making them available for other production uses.
Incremental forever backup: Rather than scheduling periodic full backups, this backup solution requires only one initial full backup. Afterwards, an ongoing (forever) sequence of incremental backups occurs. The real difference, however, is that the incremental backups are automatically combined with the original in such a way that you never need to perform a full backup again. This method reduces the amount of data that goes across the network and reduces the length of the backup window.