Copyright © Acronis, Inc., 2000-2010 103When this option is set to Enable, snapshots of all volumes being backed up will be createdsimultaneously. Use this option to create a time-consistent backup of data spanned across multiplevolumes, for instance for an Oracle database.When this option is set to Disable, the volumes' snapshots will be taken one after the other. As aresult, if the data spans across several volumes, the resulting backup may be not consistent.3.4.1.7 Volume Shadow Copy ServiceThis option is effective only for Windows operating systems.The option defines whether a Volume Shadow Copy Service (VSS) provider—either Acronis VSS orMicrosoft VSS—has to notify VSS-aware applications that the backup is about to start. This ensuresthe consistent state of all data used by the applications, in particular, completion of all databasetransactions, at the moment of taking the data snapshot by Acronis Backup & Recovery 10. Dataconsistency, in turn, ensures that the application will be recovered in the correct state and becomeoperational immediately after recovery.The preset is: Create snapshots using VSSAcronis Backup & Recovery 10 will select the VSS provider automatically based on the operatingsystem running on the machine and whether the machine is a member of an Active Directorydomain.Create snapshots without using VSSChoose this option if your database is incompatible with VSS. The data snapshot will be taken byAcronis Backup & Recovery 10. Backup process is fastest, but data consistency of the applicationswhose transactions are not completed at the time of taking a snapshot cannot be guaranteed. Youmay use Pre/Post data capture commands (p. 100) to indicate which commands should beperformed before and after taking the snapshot, to ensure that the data is being backed up in aconsistent state. For instance, specify pre-data capture commands that will suspend the databaseand flush all caches to ensure that all transactions are completed; and specify post-data capturecommands that will resume the database operations after the snapshot is taken.Volume shadow copy writersBefore backing up the data of VSS-aware applications, make sure that the volume shadow copywriters for those applications are turned on, by examining the list of writers that are present in theoperating system. To view this list, run the following command:vssadmin list writersNote: In Microsoft Windows Small Business Server 2003, the writer for Microsoft Exchange Server 2003 isturned off by default. For instructions on how to turn it on, see the corresponding Microsoft Help and Supportarticle http://support.microsoft.com/kb/838183/en.3.4.1.8 Compression levelThis option is effective for Windows and Linux operating systems and bootable media.The option defines the level of compression applied to the data being backed up.The preset is: Normal.The optimal data compression level depends on the type of data being backed up. For example, evenmaximum compression will not significantly reduce the archive size if the archive contains essentially
