Cross-region replication of Azure NetApp Files volumes
The Azure NetApp Files replication functionality provides data protection through cross-region volume replication. You can asynchronously replicate data from an Azure NetApp Files volume (source) in one region to another Azure NetApp Files volume (destination) in another region. This capability enables you to failover your critical application in case of a region-wide outage or disaster.
The cross-region replication feature is currently in public preview. You need to submit a waitlist request for accessing the feature through the Azure NetApp Files cross-region replication waitlist submission page. Wait for an official confirmation email from the Azure NetApp Files team before using the cross-region replication feature.
Supported region pairs
Azure NetApp Files volume replication is currently available in the following fixed region pairs:
- US West and US East
- US West 2 and US East
- US South Central and US Central
- US South Central and US East
- US South Central and US East 2
- US East 2 and US Central
- North Europe and West Europe
- UK South and UK West
- Australia East and Australia Southeast
- Canada Central and Canada East
- Japan East and Japan West
- UK South and Germany West Central
- Southeast Asia and Australia East
- Central India and South India
Recovery Point Objectives (RPO), or the maximum tolerable data loss, is defined as twice the replication schedule. The actual RPO observed might vary based on factors such as the total dataset size along with the change rate, the percentage of data overwrites, and the replication bandwidth available for transfer.
- For the replication schedule of 10 minutes, the maximum RPO is 20 minutes.
- For the hourly replication schedule, the maximum RPO is two hours.
- For the daily replication schedule, the maximum RPO is two days.
Recovery Time Objective (RTO), or the maximum tolerable business application downtime, is determined by factors in bringing up the application and providing access to the data at the second site. The storage portion of the RTO for breaking the peering relationship to activate the destination volume and provide read and write data access in the second site is expected to be complete within a minute.
Cost model for cross-region replication
With Azure NetApp Files cross-region replication, you pay only for the amount of data you replicate. There is no setup charges or minimum usage fee. The replication price is based on the replication frequency and the region of the destination volume you choose during the initial replication configuration. See the Azure NetApp Files Pricing page for more information.
Regular Azure NetApp Files storage capacity charge applies to the replication destination volume (also called the data protection volume).
The cross-region replication amount billed in a month is based on the amount of data replicated through the cross-region replication feature during that month. The amount of data replicated is measured in GiB. It represents the sum of data replicated across two regions during all regular replications from the source volumes to the destination volumes and during all resync replications from the destination volumes to the source volumes.
Example 1: Month 1 baseline replication and incremental replications
Assume the following situations:
- Your source volume is from the Azure NetApp Files Premium service level. It has a volume quota size of 1000 GiB and a volume consumed size of 500 GiB at the beginning of the first day of a month. The volume is in the US South Central region.
- Your destination volume is from the Azure NetApp Files Standard service level. It is in the US East 2 region.
- You’ve configured an hourly based cross-region replication between the two volumes above. Therefore, the price of replication is $0.12 per GiB.
- For simplicity, assume your source volume has a constant 0.5-GiB data change every hour, but the total volume consumed size does not grow (remains at 500 GiB).
After the initial setup, the baseline replication happens immediately.
- Data amount replicated during baseline replication:
- Baseline replication charges:
500 GiB * $0.12 = $60
After the baseline replication, only changed blocks are replicated. Therefore, only 0.5 GiB of data will be replicated every hour in the subsequent incremental replications.
- Sum of data amount replicated across incremental replications for a 30-day month:
0.5 GiB * 24 hours * 30 days = 360 GiB
- Incremental replication charges:
360 GiB * $0.12 = $43.2
By the end of Month 1, the total cross-region replication charge is as follows:
- Total cross-region replication charge from Month 1:
$60 + $43.2 = $103.2
Regular Azure NetApp Files storage capacity charge applies to the destination volume. However, the destination volume can use a storage tier that is different from (and cheaper than) the source volume tier.
Example 2: Month 2 incremental replications and resync replications
Assume you have a source volume, a destination volume, and a replication relationship between the two set up as described in Example 1. For 29 days of the second month (a 30-day month), the hourly replications occurred as expected.
- Sum of data amount replicated across incremental replications for 29 days:
0.5 GiB * 24 hours * 29 days = 348 GiB
Assume that on the last day of the month, an unplanned outage occurred in the source region and you failed over to the destination volume. After 2 hours, the source region recovered and you performed a resync replication from the destination volume to the source volume. During the 2 hours, 0.8 GiB of data change occurred at the destination volume and needed to be resynced to the source.
- Sum of data amount replicated across regular replications for 22 hours on the last day:
0.5 GiB * 22 hours = 11 GiB
- Data amount replicated during one resync replication:
Therefore, by the end of Month 2, the total cross-region replication charge is as follows:
- Total cross-region replication charge from Month 2:
(348 GiB + 11 GiB + 0.8 GiB) * $0.12 = $43.18
Regular Azure NetApp Files storage capacity charge for Month 2 applies to the destination volume.