You need to consider certain issues when planning to use SnapMirror for synchronous replication.
For more information about deduplication, see the Data ONTAP Storage Management Guide for 7-Mode.
For synchronous SnapMirror, the disks underlying the source and destination volumes should be of the same type. Also, you must ensure that the speed of the disks on the destination system is equal to, or faster than, the speed of the disks on the source system. You can have other types and speeds of disks attached to the source or destination system but the combined load of different disk types and speeds might negatively impact the performance of synchronous SnapMirror. If you face such performance issues, you might need to reduce the load on the system to resolve the issue.
|Type of volume||Data ONTAP version|
|Traditional volumes||7.2 or later|
|FlexVol volumes||7.2.2 or later|
You can choose the data to be synchronously replicated. For example, you can synchronously replicate database data and asynchronously replicate home directories. If the home directories contain important log data, you can use the synchronous SnapMirror option to replicate the log data. For more details, see the na_snapmirror.conf(5) man page.
The type of system and the disk configuration on the destination system affects the performance of the source system. Therefore, the destination system should have the bandwidth required for the increased traffic and for message logging. The NVLOG files are stored in the parent aggregate of the volume being replicated.
The network transport should be optimized for SnapMirror replication. You must use a dedicated, high-bandwidth, low-latency network between the source and destination systems. Synchronous SnapMirror can support traffic over Fibre Channel and IP transports. SnapMirror also allows multipathing, enabling you to either balance the load between two paths or to reserve the second path for failover. For optimizing performance, you can use the best route available between the source and destination systems, and you can restrict the route to the traffic between the two systems.
You should keep well below the maximum number of Snapshot copies. Synchronous SnapMirror needs three Snapshot copies to get into synchronization. Therefore, you should limit the combined total of Snapshot copies retained on any one volume to 252 or fewer.