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Wednesday, December 24, 2014

Difference between Snapmirror and Snapvault

Most of my clients had this doubt about Snapmirror and Snapvault
1) What are the differences between these two as both these perform a copy from source to destination
2) why we need to have two products for backup
3) Why do i need to buy two product license , Instead i can just have one product
4) What is my RTO and RPO with these products and which one is better for DR
Here i am trying to tell the exact difference between Snapmirror and Snapvault, First going in to basics
What is Snapvault ?

A SnapVault backup is a collection of Snapshot copies on a Flex volume that you can restore data from if the primary data is not usable. Snapshot copies are created based on a Snapshot policy. The SnapVault backup backs up Snapshot copies based on its schedule and SnapVault policy rules.
A SnapVault backup is a disk-to-disk backup solution that you can also use to offload tape backups. In the event of data loss or corruption on a system, backed-up data can be restored from the SnapVault secondary volume with less downtime and uncertainty than is associated with conventional tape backup and restore operations.
What is Snapmirror ?

SnapMirror is a feature of Data ONTAP that enables you to replicate data. SnapMirror enables you to replicate data from specified source volumes or qtrees to specified destination volumes or qtrees, respectively. You need a separate license to use SnapMirror.
You can use SnapMirror to replicate data within the same storage system or with different storage systems.
Now we see what is the difference between Snapvault and Snapmirror
First statement i would say the difference is "Snapvault is a backup solution where snapmirror is a DR solution"
Snapvault is a backup solution where we can have long snapshot retention periods on the destination filer and slower disks can be used at the destination side with low RPM's to minimize the budget , In case of disaster occurrence we can restore data from destination filer to source filer, But we cannot make the destination as source to serve the data as Snapvault destinations are READ ONLY.
Snapmirror is a DR solution where we can use Sync and Semi-Sync , Async relationships  and also we can easily restore the accidentally deleted, or lost data to source filer, if there are no updates were performed meanwhile. If there is a total disaster on the source side we can immediately perform a reverse snapmirror in case of total disaster of source we can make the destination volume/qtree as read-write and provide access to the clients. Which means low RTO and RPO , Which means low outages. Once the Source is ready we can resync the destination to source and continue with source as before.
Notable difference
Qtree SnapMirror
More suitable for providing immediate failover capability.
Uses the same functionality and licensing on the source and destination systems.
Transfers can be scheduled at a maximum rate of once every minute.
Relationships can be reversed. This allows the source to be re-synchronized with changes made at the destination.
More suitable where data availability is less critical, and immediate failover is not required.
Uses SnapVault source system and SnapVault destination system, which provide different functionality.
Transfers can be scheduled at a maximum rate of once every hour.
Snapshot copies are retained and deleted on a specified schedule.
Relationships cannot be reversed. It provides the capability to transfer data from the destination to the source only to restore data. The direction of replication cannot be reversed.
To Summarize 
Snapvault is moreover a Backup solution rather than a disaster recovery solution but imagine in case if you are  in deep trouble and need to have your production up asap then go for converting Snapvault qtree in to a Snapmirror qtree.( I haven't tried but it can be done from DIAG mode with Snapvault convert command ).
Snapmirror is purely replication solution which saves us in case of disaster.
So based on differences above we can easily judge which solution will have more RTO & RPO.
License structure was designed by Netapp , As we already know we need to have primary as well as secondary license.
Hope this helped !!