Backup solution

Posted Posted by Patrice Guay in Web hosting     Comments 1 comment
May
18

Having a process to backup your website sensitive information is a good practice to preserve your data and maintain its integrity. A backup is a copy of your data that can be used to restore the original data after a data loss caused by hardware failure, accidental deletion, data corruption, etc.

Goals and limitations

The backup of your website data should be considered as a process. Your goals in term of data recovery combined with the limitations of the backup process must be taken into account in order to implement an adequate backup solution.

Recovery Point Objective

The frequency at which the backup operation is done will influence the length of the time-gap in case of data recovery. For example, if you scheduled a weekly backup for your website database, recovering your data from the backup will roll you back in time for up to a week. Setting up your Recovery Point Objective (RPO) will help you schedule your backup operations correctly and size your backup storage accordingly.

Recovery Time Objective

On the other hand, the time required to restore your backup data in case of data loss is called the Recovery Time Objective (RTO). The choice of storage media, its location and the backup strategy will influence the recovery time. Security concerns should also be addressed by choosing an appropriate location for your storage media and using access restriction tools like encryption.

Constraints

Several limitations must be considered during the design of the backup process: performance impact, bandwidth requirements and costs are three important factors. The performance impact is the additional payload imposed on your website due to the backup operation. To minimize such performance impact, the backup operation can be scheduled when your website is seeing the least usage. The backup process will then have the least amount of interference with normal operations. You will also need to evaluate the bandwidth required during backup and restoration operations if the backup media is accessed through the network. In this common scenario, the recovery time objective (RTO) is directly related to the size of the bandwidth between your server and the backup media.

Cost is also a limitation and will guide your choice of a backup solution. All types of storage media have a finite capacity with a real cost. Matching the correct amount of storage capacity with your needs is an important part of the backup scheme design. On the other hand, using a simple scheme will help you avoid excessive labour costs. Finally, while choosing a commercial backup software may simplify the backup scheme, the cost of a proprietary solution can be important.

Storage media

Magnetic tape

Magnetic tape has been used for backup data storage for a long time. Tape is a proven storage medium, which is its main advantage along with its portability. A magnetic tape is a purely sequential access medium. While access time for random files is poor, performance for continuous writing or reading can be high. Magnetic tape features the lowest price/capacity ratio. However, the complexity of a tape backup system and the specialized hardware required for reading and writing to this medium are major drawbacks.

Hard disk

Hard disk is a common medium for storage solutions. Relying on commodity hardware, this storage technology features low access time, high capacity and a low price/capacity ratio. The main disadvantage of hard disk backups is that their portability is limited. They can be easily damaged during transport.

Solid state device

Flash memory, USB keys and USB flash drives are solid state devices that can be used for storage solutions. Their main disadvantage is their high price/capacity ratio. However, this medium offers portability, the lowest access time and ease of use.

Backup strategy

Full backup

A full backup is the first step in a rotation scheme. All the relevant data is copied on the backup media. Some backup software will allow you to restore a whole server after a full system backup is completed. This feature is called bare-metal restoration. Without this feature, the restoration of the backup data to the server will have to be executed after the restoration of the original operating system on the server.

Differential backup

A differential backup copies files and folders that have been created or modified since the last full backup. When performing a combination of normal and differential backups, the restoration will most likely require the last full backup along with the latest differential backup.

Incremental backup

An incremental backup copies files and folders that have been created or modified since the last full or incremental backup. When performing a combination of normal and incremental backups, the restoration will require the last full backup along with all the incremental backups taken in the meantime.

Rotation scheme

A complete backup strategy should include a rotation scheme to allow the conservation of historical data. Such a method is also useful for managing multiple media in the backup process. The rotation scheme determines how and when each piece of storage is used for a backup job and how long it is retained once it has backup data stored on it. A balance between the cost of extra storage media and the need for data retention must be found.

The most used rotation strategies are the Grand-Father/Father/Son (GFS) and the Towers of Hanoi. Both of these strategies use full and differential/incremental backups.

Location of the backup data

On-site

Storing the backup data on the same site as the backup target is convenient since there is no need to move backup media physically or through the network. Handling or bandwidth issues can be avoided with such a solution.

However, on-site storage is insecure. Since both original and backup data are on the same location, a major disaster (fire, flood, theft, etc.) could be catastrophic.

Off-site

Storing the backup data on a secondary location increases the reliability of the backup process at the expense of convenience. To reduce the required effort, data can be moved between both sites using the network instead of relying on the transportation of physical media.

Reference

1 Comment to “Backup solution”

  • […] array does not allow to recover a deleted or corrupted file due to a bug in your application. A backup solution will allow you to go back in time to recover deleted or corrupted […]

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