Merge pull request #107730 from fauhse/namespace-mapping

Update to Azure File Sync namespace mapping instructions

Author: American-Dipper

articles/storage/files/media/storage-files-migration-namespace-mapping/excel.png

@@ -11,7 +11,7 @@ ms.subservice: files
 
 In this step, you are evaluating how many Azure file shares you need. A single Windows Server (or cluster) can sync up to 30 Azure file shares.
 
-You may have more folders on your StorSimple that you currently share out locally as an SMB shares to your users and apps. The easiest would be to envision for an on-premises share to map 1:1 to an Azure file share. If this number is manageably small, meaning below 30 for a single Windows Server, or you plan on having two Windows Servers (60) and so on, then a 1:1 mapping is recommended.
+You may have more folders on your volumes that you currently share out locally as SMB shares to your users and apps. The easiest would be to envision for an on-premises share to map 1:1 to an Azure file share. If this number is manageably small, meaning below 30 for a single Windows Server, or you plan on having two Windows Servers (60) and so on, then a 1:1 mapping is recommended.
 
 If you have more shares than 30, it is often unnecessary to map an on-premises share 1:1 to an Azure file share.
 Consider the following options:
@@ -25,17 +25,58 @@ For instance, if your HR department has a total of 15 shares, then you could con
 Azure File Sync supports syncing the root of a volume to an Azure file share.
 If you sync the root folder, then all subfolders and files will end up in the same Azure file share.
 
-#### Other best practices to consider
+Synching the root of the volume will not always be the best answer. There are benefits in syncing multiple locations, doing so helps keep the number of items lower per sync scope. Setting up Azure file sync with a lower number of items is not just important for sync, but also benefits cloud-side restore from backups as well as aiding the speed of disaster recovery in case you lose your server and provision a new one that connects to the same Azure file shares.
 
-Other than the 30 Azure file share sync limit per server, the leading consideration is the efficiency of sync.
+#### A structured approach to a deployment map
 
-When there are multiple shares on your server each syncing to their own Azure file share, sync can work in parallel for all of them. The scale vector is not the size of all files in a sync scope. It is the number of items (files and folders) that need processing.
+Before deploying cloud storage in a subsequent step, it is important to create a map between on-premises folders and Azure file shares. This mapping will then inform how many and which Azure File Sync "sync group" resources you will provision. A sync group ties the Azure file share and the folder on your server together and establishes a sync connection.
 
-A single Azure file share can hold up to 100 TiB.
-Azure File Sync supports syncing up to 100 million items per Azure file share.
+To make the decision how many Azure file shares you need, you need to understand a few limits and best practices to optimize your map.
 
-Synching the root volume will not always be the best answer. There are benefits in syncing multiple locations, doing so helps keep the number of items lower per sync scope. Setting up Azure file sync with a lower number of items is not just important for sync, but also benefits cloud-side restore from backups as well as aiding the speed of disaster recovery in case you lose your server and provision a new one that connects to the same Azure file shares.
+* A server with the Azure File Sync agent installed, can sync with up to 30 Azure file shares.
+* An Azure file share is deployed inside of a storage account. That makes the storage account a scale target for performance numbers such as IOPS and throughput. Two standard (not premium) Azure file shares could theoretically saturate the maximum performance a storage account can deliver. If you plan to just attach Azure File Sync to these file shares with occasional direct access of the Azure file share in the cloud, then grouping several Azure file shares into the same storage account is fine. If you plan on lifting an app to Azure, that will then use the Azure file share natively, you might need more performance for this app than Azure File Sync needed from the file share. In these situations, it would be better to map an Azure file share to its own storage account.
+* There is a limit of 250 storage accounts per subscription in a single Azure region.
 
-Use a combination of the concepts above to help determine how many Azure file shares you need, and which parts of your existing StorSimple data will end up in which Azure file share.
+> [!TIP]
+> With this information in mind, it often becomes necessary to group multiple top-level folders on your volumes into a common, new root directory. You will then sync this new root directory and all the folders you grouped into it, to a single Azure file share.                                                    
 
-Create a list that records your thoughts, such that you can refer to it in the next step. Staying organized here is important as it can be easy to lose details of your mapping plan when provisioning many resources at once.
+This technique allows you to stay within the 30 Azure file share sync limit per server.
+This grouping under a common root has no impact on access to your data. Your ACLs stay as is, you would only need to adjust any share paths (like SMB or NFS shares) you might have on the server folders that you now changed into a common root. Nothing else changes.
+
+Another important aspect of Azure File Sync and a balanced performance and experience is an understanding of the scale factors for Azure File Sync performance. Obviously, when files are synced over the internet, larger files take more time and bandwidth to sync.
+
+> [!IMPORTANT]
+> The most important scale vector for Azure File Sync is the number of items (files and folders) that need to be synchronized.
+
+Azure File Sync supports syncing up to 100,000 items to a single Azure file share, which is not a hard limit, but depicts what the Azure File Sync team tests on a regular basis.
+
+It is a best practice to keep the number of items per sync scope low. That aspect is an important factor to be considered in your mapping of folders to Azure file shares.
+
+Even if in your situation a set of folders can logically sync to the same Azure file share (using the new, common root folder approach from above) it might still be better to regroup folders such that they sync to two instead of one Azure file share. This approach can be used to keep the number of files and folders per file share balanced across the server.
+
+#### Create a mapping table
+
+:::row:::
+    :::column:::
+        :::image type="content" source="media/storage-files-migration-namespace-mapping/namespace-mapping-condensed-small.png" alt-text="An example of a mapping table. Download the file below to experience and use the content of this image.":::
+    :::column-end:::
+    :::column:::
+        Use a combination of the previous concepts to help determine how many Azure file shares you need, and which parts of your existing data will end up in which Azure file share.
+        
+        Create a table that records your thoughts, such that you can refer to it in the next step. Staying organized is important as it can be easy to lose details of your mapping plan when provisioning many Azure resources at once. To help you in creating a complete mapping, you can download a Microsoft Excel file as a template.
+
+[//]: # (After several attempts, there does not appear to be a markdown way capable of adding a nested two-column table with working image parsing and text/hyperlink on the same line. HTML seems like the only option.)
+
+<br>
+<table>
+    <tr>
+        <td>
+            <img src="media/storage-files-migration-namespace-mapping/excel.png" alt="Microsoft Excel file icon that helps to set the context for the type of file download for the link next to it.">
+        </td>
+        <td>
+            <a href="https://download.microsoft.com/download/1/8/D/18DC8184-E7E2-45EF-823F-F8A36B9FF240/Azure File Sync - Namespace Mapping.xlsx">Download a namespace-mapping template.</a>
+        </td>
+    </tr>
+</table>
+    :::column-end:::
+:::row-end:::