Preparing your environment to archive backups (clustered Data ONTAP) on page 80 Preparing your environment to archive backups (7-Mode) on page 81
Preparing your environment to replicate backups
Understanding SnapManager backups with SnapMirror updates
What SnapMirror does
SnapMirror creates replicas of storage system volumes. SnapMirror can asynchronously mirror a Snapshot copy of data on a source volume to one or more volumes configured as destinations of the source volume. SnapMirror can replicate a source volume to a destination volume on the same storage system or to a different storage system. When you use SnapMirror to replicate volumes from one storage system to another, the destination storage system can be in a different geographical location. This ability to duplicate data in different locations is a key component of a sound disaster recovery plan.
The data stored in a mirror on a destination volume can be accessed through SnapDrive. Because the mirror is volume-wide, Snapshot copies of other datasets on the source volume are mirrored also.
SnapMirror updates the destination volume(s) to reflect incremental changes on the source volume.
As a result, a destination volume is an online, read-only copy of the source volume at the time of the most recent replication. This data can be used for disaster recovery, offloading tape backup, read-only data distribution, testing on non-production storage systems, or online data migration.
A SnapMirror destination volume can reside on the same storage system as the source volume or a different storage system. For disaster recovery purposes, the destination volume generally resides on a different storage system that is also geographically remote from the storage system containing the source volume. For other purposes, the source and destination volumes might exist on the same storage system.
Attention: Because SnapManager uses SnapMirror in asynchronous mode, any disk writes that occurred on the source volume after the most recent SnapMirror replication update are not available if a catastrophic failure occurs before the next update. This is because they were not replicated to the SnapMirror destination volume.
How SnapManager uses SnapMirror
SnapManager backs up your SQL Server data by creating Snapshot copies of the databases and transaction logs. SnapMirror can be used to replicate the volumes that host the Snapshot copies to mirrored volumes on a remote storage system.
How SnapManager uses SnapMirror
SnapMirror replication for SnapManager is volume replication When you use SnapMirror to replicate SnapManager backups, you can replicate only volumes, not qtrees. SnapManager does not support SnapMirror qtree replication.
Backup Snapshot can trigger SnapMirror updates SnapManager Backup uses Snapshot copy functionality to back up your SQL Server data to a storage system volume managed by SnapDrive. If the volume has been configured as a SnapMirror source volume with one or more appropriately configured destination volumes, then (upon successful completion of a Snapshot copy backup operation) SnapManager can send a request to SnapDrive to begin a SnapMirror update of each destination volume.
All three types of SnapManager Backup operations can be configured to trigger SnapMirror updates:
• Full database backup, with or without transaction log backup or database verification
• Transaction log backup only
• Database verification only
Note: The result of the database verification operation (the database integrity status) is written to the backup set, in the SnapInfo directory. By replicating the backup set to the mirrored volume, this status information is kept current on the mirrored volume.
SnapMirror replication for SnapManager is asynchronous
Preparing your environment for data protection | 75
When it is configured directly on the storage system, SnapMirror can be used to perform synchronous replication or asynchronous replication.
When you use SnapMirror to replicate SnapManager backups, however, the replication is performed asynchronously. That is, changes made to the databases between SnapManager backups are not replicated in the SnapMirror destination volume. Therefore, any restore from the destination volume restores the databases to their state at the time of the last SnapManager backup; subsequent changes to the database that occur on the source volume after the most recent SnapMirror replication update are not available if a catastrophic failure occurs before the next update of the SnapMirror destination volume.
SnapMirror scheduling When it is configured directly on the storage system, SnapMirror uses its own replication schedule as configured by a Data ONTAP administrator.
When SnapMirror is used by SnapManager, however, the SnapMirror replication schedule must be disabled on the storage system; SnapMirror updates are instead initiated by SnapDrive on the completion of a SnapManager backup operation.
Requirements for using SnapMirror with SnapManager
To use SnapMirror with SnapManager, you must have previously configured SnapMirror on both the source volume to be replicated and its destination volumes. How to complete these tasks is explained in your SnapDrive documentation. Your configuration must satisfy the following requirements:
• There must be one or more SnapMirror source volumes.
• There must be one or more SnapMirror destination volumes for each source volume.
• The size of the destination volumes must be equal to or greater than the size of the source volume.
• SnapMirror licenses must be enabled on both the source and destination storage systems.
• You must manually configure and initialize the SnapMirror replication between source and destination volumes.
• You must disable the SnapMirror replication schedule on your storage system.
• You must configure the SnapMirror replication as asynchronous.
Process overview
If your SQL Server databases reside on a storage system volume that is configured as a SnapMirror source volume, then the SnapMirror destination volume is optionally updated after the SnapManager backup operation finishes.
The following sequence provides an overview of how SnapMirror destination replication works:
1. A SnapManager backup is initiated.
2. SnapManager completes all Snapshot copies required for the backup, then requests a SnapMirror volume update through SnapDrive.
3. If any volume whose data is captured in the backup is a SnapMirror source volume, SnapDrive requests information about all SnapMirror destination volumes of that source volume.
4. SnapDrive sends a SnapMirror destination update request to all the related destination volumes.
5. SnapMirror updates the destination volumes to reflect incremental changes to the source volume.