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

The Linux Logical Volume Manager allows the creation of a snapshot of a logicalvolume while the logical volume itself is still online. The snapshot is created insidethe same volume group as the source logical volume. You must ensure that thevolume group provides enough free disk space to create the snapshot. Thesnapshot contains the old data blocks while the modified data is stored in thesource logical volume. Use the snapshotcachesize option with the backup imagecommand, in the dsm.opt file, or with the include.image option to specify anappropriate snapshot size so that all old data blocks can be stored while the imagebackup occurs. A snapshot size of 100 percent will ensure a valid snapshot. See“Snapshotcachesize” on page 350 for more information.Utilizing image backup to perform file system incrementalbackupThere are two methods of utilizing image backups to perform efficient incrementalbackups of your file system. These backup methods allow you to performpoint-in-time restore of your file systems and improve backup and restoreperformance. You can perform the backup only on formatted volumes; not on rawlogical volumes. You can use one of the following methods to perform imagebackups of volumes with mounted file systems.Method 1 Using image backup with file system incremental:1. Perform a full incremental backup of the file system, for example:dsmc incremental /myfilesystem2. Perform an image backup of the same file system, for example:dsmc backup image /myfilesystem3. Periodically, perform incremental backups, for example:dsmc incremental /myfilesystemYou must follow these steps in the order shown to ensure that the serverrecords additions and deletions accurately.4. The following command restores the file system to its exact state as of the lastincremental backup:dsmc restore image /myfilesystem -incremental -deletefilesDuring the restore, the client does the following:v Restores the most recent image on the server.v Deletes all of the files restored in the previous step which are inactive on theserver. These are files which existed at the time of the image backup, butwere subsequently deleted and recorded by a later incremental backup.v Restores new and changed files from the incremental backups.If you do not follow the steps exactly, two things can occur:v After the original image is restored, all files backed up with the incrementalcommand are restored individually.v If you perform a backup image before performing an incremental, files deletedfrom the original image are not deleted from the final restored file system.Method 2 Using image backup with image incremental mode:1. Perform an image backup of the same file system, for example:dsmc backup image /myfilesystem2. Perform an incremental image backup of the file system, for example:dsmc backup image /myfilesystem -mode=incrementalChapter 10. Using commands 407