In part 1 of these series we discussed the merits of Azure file sync. One of the options of this technology is Cloud tiering. This feature of Azure File Sync in which frequently accessed files are cached locally on the server while all other files are tiered to Azure Files based on policy settings. When a file is tiered, the Azure File Sync file system filter replaces the file locally with a pointer, or reparse point. In the event a user needs a file which has been cached, Azure File Sync quietly downloads the file from Azure Files from the cloud.

There are two fundamental policies which are available for tiering:

• Volume of free space
• Date

Volume free space policies always takes precedence over any other policies, including the date policy. Optionally, you can enable a date policy for each server endpoint on that volume. Regardless of the precedence, the results are similar: when a threshold is met, it will tier the file replacing the file with a reparse point which represents a URL to the file in Azure Files. 

One aspect of the Azure files sync which should be noted (regardless of Tiering option) is that the Storage account will maintain a complete copy of the share data. Because of this, Azure owners can take advantage of an Azure Vault to completely backup the storage account.

Key features of this which would be advantageous to companies:

• No infrastructure is required for Azure Vault.
• Private end points can be used to control access between the Azure Vault and the Storage account to prevent exposure on the internet. (This will be discussed in part 3 of this series)
• Both general purpose version 2 (GPv2) and FileStorage storage accounts work natively with Azure Vault. Both storage account varieties to use, both support 100 TiB shares, however only the FileStorage storage operates on SSD if the performance is required. An example of this would be Office content for a large company with a high rate of churn.
• Soft deletion protection: This feature will protect against accidental deletions. Currently Azure admins specify a retention period between 1 and 365 days. You can change the soft delete retention period at any time. 

In this blog we discussed the storage and backups considerations which are related to getting Azure File Sync Online. The 3^rd part of the series we will explore the networking aspects for consideration.