In this article, we look at how reliability for backups can be increased with the use of Backup Media sets that are mirrored.
Mirroring with a media set drastically increases the reliability of a backup by reducing chances as well as the fallout of device malfunctions. Mirroring is an essential function of SQL server as a backup is the last ray of hope which can protect the user against possible data loss. In time as the data grows, the probability of malfunctions also grows which increases the risk of failure in backup devices. Sometimes backup can also become non-restorable because of miscellaneous reasons. In a situation like this, mirroring comes in for rescue. Opting for Mirroring backups can help businesses in increasing reliability by providing significant redundancy to the backups.
Key Benefits of Mirrored Backup Media Sets
1. Share Media File with Media Families
A mirrored set comprises of numerous copies or mirrors of different media sets. Any given media set can contain one or multiple media families, in which each of them relates to a particular backup device. Let’s take an example, if a TO clause lists three devices in its BACKUP DATABASE statement, then BACKUP will spread this data across three media families, listed here. The number of mirrors and media families are defined, when a user creates a media set (with a BACKUP DATABASE statement which specifies WITH FORMAT).
2. Store up to 4 Mirrors in one Media Set
A mirrored media set can possess starting from two to as many as four mirrors. It is important to note that each of these mirrors contains every media family available in the media set. Note that mirrors need the same number of database devices, for creating backups one by one for each media family. Each mirror can create a backup for one media family in one backup device. For example, there is a set of mirrored media which consists of three media families comprising of three mirrors but requires over twelve backup devices. All these devices need to be exactly equivalent. So as to say, tape drives with the same model number which belong to the particular manufacturer.
3. Mirror Splitting and Data Damage
A user can not split or break any mirrored media or remove a mirror. Just in case any disk or tape in a mirror reformatted, or is damaged, the mirror will be no longer be usable for any additional backups. However, if in case even one full mirror manages to remain intact, then the media set will be in readable condition. If every mirror ends up losing its given media family, then media set will become useless.
Backup or restore operations work based on different requirements based on whether every mirror should be present or not. For writing a backup operation for (to essentially create or attempt to extend) a given mirrored media set, it is critical that all mirrors should be present in the backup. In stark contrast, when a user is restoring any backup using a set of mirrored media, he/she can specify one mirror only for each media family. However, in the presence of any errors, having another mirror enables certain restoration problems to resolve quickly. Users can also substitute the volume of a damaged media with the corresponding volume from any other mirror. Further invest in an mdf fix tool to drastically reduce chances of data loss.
Victor Simon is a data recovery expert in DataNumen, Inc., which is the world leader in data recovery technologies, including access recovery and sql recovery software products. For more information visit www.datanumen.com