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| 1 | +--- |
| 2 | +title: Azure File Sync Throttling Limits |
| 3 | +description: Understand how Azure File Sync integrates with Azure Throttling Service (ATS) to implement throttling on key APIs to protect against unexpected load surges. |
| 4 | +author: khdownie |
| 5 | +ms.service: azure-file-storage |
| 6 | +ms.topic: how-to |
| 7 | +ms.date: 10/15/2025 |
| 8 | +ms.author: kendownie |
| 9 | +# Customer intent: "As an IT administrator, I want to understand Azure File Sync throttling behavior so I can avoid throttling and maintain optimal performance for my file shares." |
| 10 | +--- |
| 11 | + |
| 12 | +# Understand Azure File Sync throttling |
| 13 | + |
| 14 | +Azure File Sync now integrates with Azure Throttling Service (ATS) to implement throttling on key APIs to protect against unexpected load surges. This article explains how throttling works for Azure File Sync, and lists the throttling limits for the resource provider and storage sync service. |
| 15 | + |
| 16 | +## Azure Resource Manager (ARM) throttling behavior |
| 17 | + |
| 18 | +Azure Resource Manager [implements throttling](/azure/azure-resource-manager/management/request-limits-and-throttling) at two levels: subscription and tenant. This is done to manage the number of requests made to Azure services, ensuring fair usage and preventing overloading. If requests are within the limits for these levels, they are routed to the resource provider. |
| 19 | + |
| 20 | +## Azure File Sync throttling behavior |
| 21 | + |
| 22 | +Azure File Sync uses the Microsoft.StorageSync resource provider, which applies its own throttling limits. |
| 23 | + |
| 24 | +Azure File Sync enforces throttling in two ways: |
| 25 | + |
| 26 | +- Regionally at the scope of individual resource types, such as storage sync service, registered server, sync group, cloud endpoint, or server endpoint. If too many operations are performed on a specific resource such as a server endpoint, further actions on that resource are temporarily blocked until the throttling period ends. |
| 27 | + |
| 28 | +- Using the storage sync service resource as a scope. Excessive operations across resources within a storage sync service will result in a temporary block on all resources under that service until the enforcement period expires. |
| 29 | + |
| 30 | +By throttling in this manner, we can better control consumption of our APIs to protect customers from potential outages. |
| 31 | + |
| 32 | +## Per-resource limits |
| 33 | + |
| 34 | +The following table lists the per-resource limits for Azure File Sync. |
| 35 | + |
| 36 | +| Operation type | Examples | Limit | Enforcement length | Refill rate | |
| 37 | +|---------------------------------------------|--------------------------------------------------------------------------|-------|-------------------|------------------| |
| 38 | +| PUT requests | Creating a server endpoint | 12 | 3 minutes | 4 tokens/min | |
| 39 | +| PATCH requests | Enabling/disabling tiering on a server endpoint, or updating tiering policies | 12 | 3 minutes | 4 tokens/min | |
| 40 | +| DELETE requests | Deleting a server endpoint | 12 | 3 minutes | 4 tokens/min | |
| 41 | +| GET requests | Browsing a server endpoint resource in the Azure portal | 400 | 3 minutes | ~2 tokens/s | |
| 42 | +| GET list requests | Browsing the list of server endpoints under a sync group in the Azure portal | 1800 | 3 minutes | ~10 tokens/s | |
| 43 | +| Cloud endpoint trigger change detection request\* | Triggering change detection on a specific cloud endpoint | 5 | 30 minutes | 1 per 6 mins | |
| 44 | + |
| 45 | +\*The trigger change detection feature for cloud endpoints is powerful, but also resource-intensive. Running it too often can slow things down and even cancel previous operations. For this reason, we’ve set a specific limit to ensure the system has enough time to process each request. |
| 46 | + |
| 47 | +## Storage sync service limits |
| 48 | + |
| 49 | +The following table lists the per-storage sync service limits for Azure File Sync. |
| 50 | + |
| 51 | +| Operation type | Examples | Threshold | Enforcement length | Refill rate | |
| 52 | +|------------------|------------------------------------------------------|-----------|--------------------|---------------------| |
| 53 | +| PUT requests | Creating resources under a storage sync service | 450 | 3 minutes | 25 tokens per 10s | |
| 54 | +| PATCH requests | Updating resources under a storage sync service | 450 | 3 minutes | 25 tokens per 10s | |
| 55 | +| DELETE requests | Deleting resources under a storage sync service | 450 | 3 minutes | 25 tokens per 10s | |
| 56 | +| GET requests | Getting individual resources under a storage sync service | 10,000 | 3 minutes | ~55 tokens/s | |
| 57 | +| GET list requests| Getting lists of resources by resource type under a storage sync service | 12,000 | 3 minutes | ~66 tokens/s | |
| 58 | + |
| 59 | +## Frequently asked questions about throttling |
| 60 | + |
| 61 | +The following are common questions about throttling in Azure File Sync. |
| 62 | + |
| 63 | +- **What's the reasoning behind these limits?** |
| 64 | +- Azure File Sync is designed for reliability and smooth operation. Most customers only need to make a few changes at a time, such setting up resources or adjusting settings. That’s why limits on actions like creating, updating, or deleting resources are set fairly low. This helps prevent accidental overloads and keeps the service running smoothly. |
| 65 | + |
| 66 | +- **What about normal operations like browsing files and reading data?** |
| 67 | +- You can freely browse and read your resources in the Azure portal or programmatically. The limits for these operations are generous, so you shouldn’t run into issues during normal use. |
| 68 | + |
| 69 | +- **What happens if you hit a limit?** |
| 70 | +- If you reach a throttling limit, further actions on that resource will be temporarily paused. Once the throttling period ends, you’ll be able to continue as normal. |
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