Specifications

NetApp Deduplication for FAS and V-Series Deployment and Implementation Guide
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As a best practice, NetApp recommends performing qtree SnapMirror updates after the deduplication
process on the source volume has finished running. If a qtree SnapMirror update occurs while the
deduplication process is running on the source volume, then in addition to the transfer of the changed data
blocks, some unchanged data blocks might also get transferred to the destination. If deduplication is not
running on the destination volume, then the redundant data that is transferred occupies extra storage space
on the destination volume.
NetApp also recommends that if deduplication is used on the source volume, then it should also be used on
the destination volume. However, you don’t have to use deduplication on the source volume if you are
planning to use deduplication only on the destination volume.
As far as the qtree SnapMirror base Snapshot copy is concerned, there are typically only a couple of
Snapshot copies on the destination storage system. If Snapshot copies are not retained long term, they are
constantly rotated out and the deduplicated blocks are freed as the Snapshot copies roll off.
If users want to keep Snapshot copies long term (as a replacement for SnapVault, or for other reasons such
as the ability to have writable, reverse, or resync copies in the event of a disaster), it is possible that
deduplicated data can be locked in Snapshot copies for longer periods of time, which reduces the
deduplication storage savings. This situation can arise when users create Snapshot copies manually or by
using snap sched.
The best practice when using qtree SnapMirror with deduplication is to let qtree SnapMirror use the
minimum number of Snapshot copies it requires (essentially, keep the latest version).
Qtree SnapMirror Replication with Deduplication Enabled on the Source Only
A source deduplicated flexible volume can be replicated to a nondeduplicated volume on the destination by
using qtree SnapMirror, as shown in Figure 4.
Figure 4) Qtree SnapMirror replication from a deduplicated source volume to a nondeduplicated destination
volume.
Keep the following points in mind:
Deduplication is licensed only on the source system.
Deduplication is enabled, run, and managed on a flexible volume at the source.
Deduplication doesn’t yield any network bandwidth savings because qtree SnapMirror works at the
logical layer, and it sends undeduplicated data over the network.
The deduplication schedule is not integrated with the qtree SnapMirror update, and vice versa; it must
be configured independently. The completion of a deduplication process doesn’t automatically start a
qtree SnapMirror transfer, and qtree SnapMirror updates don’t trigger the deduplication operation.
Deduplication storage savings are achieved only on the source system.