Learn about FSx for ONTAP FlexCache Write-back

Kanako Kodera — Fri, 13 Jun 2025 06:48:53 +0000

Today I’ll introduce a new feature of Amazon FSx for NetApp ONTAP, the Writeback mode of ONTAP FlexCache.
AWS What's new
This feature was originally offered in ONTAP version 9.15.1 and later and is now available on AWS at no cost.

About ONTAP FlexCache

ONTAP FlexCache is a mechanism that temporarily stores data from the original volume (origin volume) in a cache volume in a different location so that users can access the data from that cache at high speed.
Protocols are available for both SMB (Windows) / NFS (Linux).

Faster Reads
By caching frequently accessed data locally, read performance is greatly improved.
Bandwidth savings
Reduces access across the WAN, minimizing network bandwidth usage.
Distributed access
Even when the same data is accessed at multiple locations, caches can be placed at each location.
Automatic Synchronization
Changes to the origin volume are reflected in the cache as needed.
Read-only or read/write support
FlexCache is basically read-only, but can also be written under certain conditions.

Use Case #1

Utilize data in the cloud with on-premise as the origin

On-premise machine groups access on-premise ONTAP
When on-premises compute resources are insufficient, cache storage in the cloud and read data from cloud compute resources at high speed (Cloud Bursting)

Use Case #2

On-premises caching of cloud file servers

Compute resource in the can access Amazon FSx for NetApp ONTAP
ONTAP is installed on-premises as cache storage
On-premises machines access ONTAP cache storage and read data at high speed

This configuration is useful when the access speed from on-premises to the cloud is not fast enough.

Use Case #3

Data collaboration and aggregation between locations

Cache storage is placed at branch offices for high-speed access to headquarters data from branch offices for corporate use.
Original data is centralized at the headquarters and managed centrally.

Detailed in FlexCache WriteBack

Write-back mode is a new ONTAP capability that helps you achieve faster performance for your write-intensive workloads that are distributed across multiple AWS Regions and on-premises file systems.

Write-back from cache to origin happens asynchronously. This means that dirty data isn't immediately written back to the origin.

FlexCache write-back involves many complex interactions between the origin and caches. For optimal performance, you should ensure your environment follows some requirements or guides that NetApp provides based on official document.

When is this effective?

Distributed file systems can be realized.
It's possible to improve performance at near-local speeds for specific workloads and environments, resulting in significant performance benefits, as for the case of content creation, distributed databases, and engineering workflows that need to operate across multiple AWS Regions or between cloud and on-premises environments.

ONTAP FlexCache write-back prerequisites

The origin must be running ONTAP 9.15.1 or later.
Please check the latest document

DEV Community: Kanako Kodera