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How Data ONTAP Snapshot copies work in an iSCSI or FC network

If you take a Snapshot copy of a file system when an application is running, the Snapshot copy might contain inconsistent data. You can take measures (such as quiescing the application) to ensure that the data is consistent before you take the Snapshot copy.

To take a Snapshot copy of these types of applications, you should ensure that the files are closed and cannot be modified. When you quiesce an application or take it offline, the file system caches are committed before the Snapshot copy is taken. The Snapshot copy takes less than one second to complete, after which the application can resume normal operation.

Some applications take a lot of time to quiesce. To avoid a scenario in which the application is unavailable for a long time, some applications have a built-in hot backup mode. This allows a Snapshot copy or a backup to occur while the application operates in a degraded mode, with limited performance.

Data ONTAP cannot take Snapshot copies of applications that have the ability to work with raw device partitions. You should use specialized modules from a backup software vendor tailored for such applications.

To back up raw partitions, it is best to use hot backup mode for the duration of the backup operation. For more information about backup and recovery of databases using SAN configurations, see the appropriate technical report for the database.