Most companies, big or small have faced some sort of a database disaster some time or the other. Hence, it becomes extremely important to have the right sort of backup strategies for servers and database to be in place. Before one decides on the right backup strategy, it is of extreme importance to know the answers to some questions pertinent to the servers. The most important question is 'what is the maximum permissible downtime which will be tolerated?' Depending on the answer to this question, you will be able to find the right strategy.
Server Backup Strategies
For servers it is important to have a backup in place. It is the only method, which will ensure that critical data is safe. In case of an untoward incident, it should be possible to restore the data with minimum amount of downtime. There are different types of backup strategies for your system and also for the server, that can be used. The right strategy will depend on the work schedule of the company and also the space available for taking the backup.
Full System Backup
One of the backup strategies for small business or for home networks is the use of full system backup. It is the safest of the backup systems, as in this system, all the files and directories on the server are backed up. In other words, a duplicate copy of the server is created. In case of a crash or virus attack, the entire server can be restored without loss of data. Taking a full backup takes substantial amount of time, hence this strategy is not adopted on a daily basis.
Depending on the amount of data on the server the backup is taken either once a week or once a month. There is a disadvantage of using this strategy. In case the backup data storage is stolen or misplaced, then it can be a threat to the company, as the data can fall in the hands of miscreants or opponents.
It is one of the backup strategies for home networks as well as for large networks. Taking this backup is rather faster. As the name suggests, in this strategy, backup is taken only for those data files that have undergone a change, since the last full or incremental backup was taken. Therefore, the time required for this type of backup is very less as compared to that of a full system backup.
The 'archive bit' functionality of the backup software is used to check if the file is not backed up twice, in case the file is moved from one location on the server to the other. In incremental backup the archive bit is removed, due to which once a file is backed up, there is no duplicate backup of files.
In the differential backup system, the files that have undergone a change since the last full backup are taken. The disadvantage of differential backup is that it does not change the archive bit setting. Therefore, the data that has undergone change since the last full backup is backed up twice leading to wastage of memory space. However, there is also an advantage of using this backup strategy. Only the full back up storage media along with the differential storage media are needed for the system to be restored.
Synthetic Full Backup
This is the backup strategy implemented, when the backup window between the previous full backup or incremental or differential backup is small. In this backup strategy, the software will seek information from the previous full backup and incremental and/or differential backup. With the difference from the previous backup, full backup is created. The most important advantage of this backup is that it does not disrupt the tasks that are being carried out on the server, when the backup is being taken.
If there is a transactional or real-time database server, then it is important to back up every transaction that has taken place. This is where the continuous backup strategy is used. Every small change that takes place on the server is captured and is stored on a separate location. Therefore, in case of any problem to the database, the server can be restored totally at any given point right up to the last save on the server, before the problem occurred.
This backup strategy is similar to continuous backup. The difference lies in when is the backup taken. In snapshot, the system backup is taken at regular intervals, which can be every few minutes. However, there is a disadvantage of this system. Snapshots rely completely on the pointers on the servers. If the pointers are removed or get deleted, then the backup may not be taken.
Like is the case with continuous backup, it does not take long to take a snapshot and the server can be restored easily. It can also be used for re-creating point of time disk states in case of a problem. However, at this point I would also like to bring to your notice, that snapshot is not exactly a backup and a backup of the snapshot has to be created to protect the data.
When one talks about server backup strategies or backup for home system the data repository has an important role to play. The data that is backed up has to be stored in an organized manner. Different types of computer data storage devices are used to back up the servers. The type of storage device will depend on the amount of data being stored.
The frequency of the backup will depend on the servers backup strategy used as well as need of the backup. In most cases, servers are backed up once at night. Often one full backup is taken once in a week and it is backed with incremental backup taken everyday. It is important to store the back up storage device stored on another physical location to protect the data not only from theft, but also other accidental damages.