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UPDATE: This post has been updated to provide more details on Azure File Sync (AFS), its strengths gaps, and limitations, and how it compares to HubStor. 

Azure File Sync (AFS) was announced at Microsoft Ignite 2017. At HubStor, we are often asked about AFS. Some people want to use it with HubStor. For others, it is a choice of HubStor or AFS.

In this post, we provide insights to help you differentiate Azure File Sync and HubStor, and how you can optionally combine the two solutions in your storage transformation strategy.

What is Azure File Sync?

Azure File Sync (AFS) is an easy way to integrate multiple Windows Servers into a global namespace. In other words, you can have multiple instances of Windows Servers synchronizing their data and permissions to Azure File Services in the cloud. This provides a common file server with synchronized directory structure, permissions, and data for a distributed workgroup.

Setting up AFS is incredibly simple. The first step is to create and configure a Sync Group in Azure. Next, you need to enroll one or more Windows Server instances into the Sync Group. The enrolment process includes running an installer on the Windows Server host machine to deploy the Microsoft sync engine software and filter-driver component.

Global Namespace for Workgroups

The global file share concept is particularly useful for remote and branch office scenarios.

At the time of launch, Azure File Sync supported five (5) Windows Server instances in a sync group only. But as everyone expected, Microsoft has increased this number significantly.

The sync engine initially did not include the concept of global file locking, but global file locking is a highly anticipated feature for AFS.

The Cloud Storage Tiering Advantage

In addition to providing a global namespace, the filter-driver component of Azure File Sync performs seamless storage tiering. Original files can be converted to offline files with reparse points that support intercepting file open requests.

This method of storage tiering is handy because any user or application will continue to see tiered files as if they are local, and they can open and interact with files as normal.

Since the data must exist in the cloud to sync across all the Windows Servers in the Sync Group, it makes sense to virtualize the older data because it isn’t being accessed. The result is a lean and mean on-prem Windows Server and significantly less load on the network connection – the sync engine creates the older data on-prem as offline files as opposed to downloading everything to all Windows Servers.

How Pricing Works

AFS uses Azure Files storage in Azure. Coinciding with the public preview announcement during Ignite 2017, Microsoft included a 25% price reduction of Azure File Services when configured as Locally-Redundant Storage (LRS), bringing monthly storage costs down to $0.06/GB/month. As usual, prices can vary depending on the Azure region you use. And if you opt for Geo-Redundant Storage (GRS), Azure Files comes in at $0.10/GB/month plus the $0.02/GB geo-replication bandwidth cost.

While monthly per gigabyte storage costs are going to the major cost component with AFS, they are certainly not the only cost factor. As with most cloud infrastructure, there are multiple cost variables at play. The total cost of AFS is determined by the following variables:

  1. The number of servers that connect to the Azure Files cloud endpoint – $5 per month for each enrolled server;
  2. The underlying costs of File storage, which include:
    • Monthly storage costs per gigabyte ($0.06 to $0.10 depending on replication level), and
    • Storage operations costs – these vary depending on region and replication level, but you have tiny costs associated with write, list, and read operations (e.g. $0.03 per 10,000 operations);
  3. Outbound data transfer – Egress bandwidth costs per gigabyte vary depending on the region hosting your Azure Files storage, anywhere from $0.08 to $0.12. There’s also built-in volume discounts (the more you download the cost per gigabyte rate reduces).

Finally, if you want to backup your data in the cloud, with Azure Files you can implement a do-it-yourself approach with AzCopy or Powershell. You’ll be able to keep a safe copy in a second storage account. Obviously, the storage and storage operations costs (and egress bandwidth if the secondary account is in another region) should be factored into your cost model also.

Azure File Sync vs. HubStor’s Cloud Data Management Platfom

Azure File Sync competes more with cloud storage gateway solutions such as Nasuni or Panzura. Compared to HubStor, AFS is more complementary than it is competitive. However, if you use HubStor, the only reason you would use AFS is for the global namespace capability. As we will see, HubStor does everything else and much more.

For small businesses with just two or three terabytes, we think Azure File Sync is an ideal fit. Using AFS, a small business can easily cloud-enable their Windows Servers and, since their storage volumes are so low, not worry too much about the higher storage cost of Azure Files. For smaller organizations that already have a Windows Server storage infrastructure, AFS is particularly attractive compared to the prospect of acquiring and deploying new cloud storage gateway appliances that require a lift and shift. And compared to HubStor, there isn’t the compute costs of a single-tenant SaaS deployment.

However, in scenarios with storage requirements exceeding 20 TB, we think IT administrators will need to consider their options more closely.

The two largest problems you’ll find with AFS are the size limits of an Azure Files share and the high monthly cost per gigabyte rate of Azure Files. You can’t scale the cloud storage component and, even when you can (assuming the limits will increase), the economics of Azure Files is not ideal for large-scale storage footprints.

The following chart provides a comparison of AFS to HubStor:

Azure File Sync HubStor Cloud Data Management Platform
Global namespace Yes  No
Cloud tiering for Windows Servers Yes Yes
Deterministic policy controls for cloud tiering No Yes
Storage tiering for CIFS/NFS  No Yes
Support for Windows Data Deduplication Drives  No Yes
Number of Windows Servers supported per configuration (sync group/tenant) 50 Unlimited
Fast recovery of data using offline files instead of full download  Yes Yes
Granular control of bulk recovery capabilities No Yes
Available in all Azure regions No Yes
Backend Azure storage type Azure Files Azure Blob Storage
In-cloud storage tiering No Yes (policy-driven tiering from Hot to Cool to Archive)
Cloud storage scalability limit 5 TB per share but supports up to 20 accounts so with striping you can achieve 100 TB capacity. Hundreds of Petabytes (5 PB per Azure Blob Storage account; HubStor can scale out to have multiple storage accounts)
Supports both domain joined and non-domain joined servers simultaneously No Yes
Windows file system formats supported NTFS NTFS, ReFS, FAT, FAT32
Works with Windows Server versions: Windows Server 2012 R2, 2016, and 2019 Windows Server 2003, 2008, 2008 R2, 2012, 2012 R2, 2016, and 2019
Works with servers that have sysprep No Yes
Azure AD integration with directory synchronization No Yes
Azure AD integration has all on-premises apps authenticating No Yes
Web-based user portal for self-service access as business continuity feature No Yes
Admin Portal with chargeback reporting No Yes
Max. file size supported 1 TB Unlimited file size (seriously)
Max. number of file system objects (directories and files) in a directory 200,000 (hard limit) 4.2 billion
Maximum object (directories and files) name length 255 characters (hard limit) 32 KB (long path supported)
In-place file analytics in the cloud No Yes
Activity auditing No Yes
Granular RBAC for privileged user access to web-based Admin Portal No Yes
Fully-managed cloud infrastructure No Yes
Legal hold No Yes
Data classification No Yes
Keyword search for discovery and end users No Yes

AFS is a hybrid cloud file collaboration solution that can enhance your storage management and backup strategies. However, due to many of its limitations and gaps, organizations with large data volumes and enterprise IT configurations are unlikely to adapt to it. At HubStor, we like to recommend AFS as a convenient method for addressing the global namespace requirement, and to let HubStor deal with the scalable storage backend and long-term retention aspects. Of course, if you aren’t concerned about the global file share capability, and you are dealing with large directories and long file names, and you want better storage economics in the cloud, then HubStor is probably all you need.

Why Azure File Sync Needs an Azure Archive Strategy

AFS, just like any collaboration solution, requires you to think about data management and archiving because aging data eventually clutters and burdens the workspace.

As you consider using AFS, we recommend planning your data management strategy in parallel, which will be driven by three factors:

  • Cost management – moving older data from Azure Files storage to lower-cost Azure Blob Storage will reduce cloud storage spending. In the archive, HubStor’s storage analytics and policy engine make it easy to manage data between Hot, Cool, and Archive tiers for further cost optimization.
  • Performance and efficiency – minimizing the file object count that the sync engine needs to manage will eventually become a priority in order to allow the sync engine to run more efficiently.
  • Data governance requirements — AFS uses Azure Files which is readily available storage for other services to run against the data. However, a proactive cloud data management strategy may be better for some clients. For instance, search and data classification features support fast discovery for legal and data privacy scenario. Other features such as chargeback and the eventual deletion of content are turn key with analytics, reporting, and policy controls. Features like WORM storage and litigation hold are also available in HubStor but not AFS.

Cost Analysis: Azure Files vs. Azure Blob Storage with HubStor

As we touched on earlier, there is quite a spread in pricing between Azure Files and Azure Blob Storage. The pricing for Azure Files is well suited for active data; whereas, Azure Blob’s Cool and Archive tiers are nicely suited for long-term retention of data that is low-touch.

To illustrate this difference, we have run the monthly figures comparing the pricing of AFS and HubStor at data volumes from 1 TB up to 210 TB.

AFS Blog Pricing Chart - updated


  • Azure pricing is based on East US 2 region in USD, pay-as-you-go rates.
  • No storage access/activity or data egress costs are factored.
  • For Azure File Sync:
    • Five (5) Windows Servers in the sync group up to 105 TB.
    • At 105 TB and beyond, 10 Windows Servers in the sync group (we assume Microsoft will support larger sync groups in the future).
  • For HubStor:
    • At 15 TB, the performance class of the PaaS configuration is increased to S2.
    • At 105 TB, the performance class of the PaaS configuration is increased to S3.
    • The figures are all inclusive of Azure costs and HubStor’s standard markup.

It is important to also call out the fact that the above price examples do not factor the activity costs.

Storage activity costs are often overlooked, and they can be significant with object counts into the hundreds of millions or billions of items.

As you can see in the chart below, a sample of the storage access costs for Write, List, and Read operations is significantly lower in Azure Files than what we see with Azure Blob.

AFS – LRS AFS – GRS Hot Blob – LRS Hot Blob – GRS Cool Blob – LRS Cool Blob – GRS Archive Blob – LRS
Write Operations (per 10,000) $0.015 $0.03 $0.05 $0.10 $0.10 $0.20 $0.30
List Operations (per 10,000) $0.015 $0.015 $0.05 $0.10 $0.10 $0.20 $0.30
Read Operations (per 10,000) $0.0015 $0.0015 $0.004 $0.004 $0.01 $0.01 $0.15

Microsoft is pricing higher activity costs on the lower-cost storage tiers.

A pricing structure like this means that you need to manage data intelligently to have optimally storage spend in the cloud. Analytics and a sophisticated rules engine allow you to place data on the appropriate tier at the best time.


So far, we have looked at the cool new Azure File Sync from Microsoft. We think it is a great fit for many types of organizations and scenarios, and ultimately will help drive adoption of the Azure cloud platform.

Unfortunately, for cloud storage gateway vendors, AFS is another bite into their total addressable market. In a previous post, I commented on Gartner’s negative view on the CSG market. AFS is just another reason why it is a tough to be a CSG vendor these days.

Although Azure File Sync is a great solution for a cloud file share and global namespace, it is not yet ready for scalability enterprise scenarios. The storage costs of Azure Files becomes prohibitive as your data volumes grow. For these reasons, we think AFS is either a small business play, or for enterprises to use alongside HubStor.

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