IBM Tivoli Storage Manager for UNIX and Linux Backup-Archive ...

Table 26. Planning your backups (continued)hhIf you are performing an image backup, ensure that you have accounted forunique considerations. See “Performing an image backup” on page 137 for moreinformation.For further backup considerations, see “Backup (UNIX and Linux): Additionalconsiderations” on page 157.When to back up and when to archive filesWhen the backup-archive client backs up or archives a file, it sends a copy of thefile and its associated attributes to the server; however, backups and archives havedifferent goals. Use backups to protect against unforeseen damage to your files,and use archives for maintaining more permanent versions of your files.Backup data is managed by version, using predetermined policy based rules. Usingthese rules, the Tivoli Storage Manager administrator can control the following:v The number of versionsv The number of days each additional backup copy is keptvWhat happens to backup data versions when the file is deleted on the clientsystemEach copy of the file stored on the server is considered to be a separate and uniqueversion of the file.Archive is a powerful and extremely flexible mechanism for storing long termdata. Archive data is kept for a specified number of days. Archive has no conceptor support for versions. The user or Tivoli Storage Manager administrator isresponsible for determining what files get added to an archive.Recommendation: If archive is run multiple times against a file using the samearchive description, a new copy of the file will be added to the archive each timethat archive is run. To simplify retrieve, store only one copy of a file in eacharchive.Backups protect against file damage or loss that could occur through accidentaldeletion, corruption, disk crashes, and so forth. The server maintains one or morebackup versions for each file that you back up. Older versions are deleted asnewer versions are made. The number of backup versions the server maintains isset by your administrator.Note: If you frequently create archives for the same data, consider using instantarchives (backup sets) instead. Frequent archive operations can create a largeamount of metadata in the server database increasing database growth anddecreasing performance for operations such as expiration.Archive copies are saved for long-term storage. Your administrator can limit howlong archive copies are kept. The server can store an unlimited number of archiveversions of a file. Archives are useful if you need to go back to a particular versionof your files, or you want to delete a file from your workstation and retrieve it at alater time, if necessary. For example, you might need to save spreadsheets for taxpurposes, but because you are not using them, you do not want to leave them onyour workstation.106 IBM Tivoli Storage Manager for UNIX and Linux Backup-Archive Clients Version 6.1: Installation and User’s Guide