Starting with Resilio Connect v2.10 Agents' support system integrated Selective Sync functionality which is based on a special Windows API. It comes to replace the legacy Selective Sync.
It allows access and downloads files directly using a file browser or transparently through an application. Some limitations in usage flow apply, see them listed below.
To enable it for an Agent put the option "Advanced selective sync" to true in the Agent profile. Before doing it, it's advisable to remove the Agent from the job and add it back after enabling the option.
The Archive does not store file versions for TSS folders
The Archive does not store file versions. Only the files deleted on remote Agents are moved to the Archive in a TSS folder. See below for more details.Don't run two Agents with Selective Sync on the same computer
Running two Agents, with at least one of them is in Transparent Selective Sync mode, on the same computer is not supported and is highly not advisable.Possible conflict with One-Drive
Configuring Agent to sync a One-Drive folder with 'on demand' files won't work - these files won't be uploaded and the job won't be completedThe optimal number of files for TSS
It's advisable not to use TSS for folders with more than 10 million files in sum. Performance degradation and synchronization issues will be observed.SYSTEM REQUIREMENTS
Advanced selective sync works only on:
- Windows 10 20H2 (OS build 19042) and newer
- Windows Server 2022 (21H2) or newer with desktop experience (from release channel LTSC)
Please check for file C:\Windows\System32\cldapi.dll existence as a quick check if your Windows supports the advanced selective sync.
Works for local NTFS, which can be accessed via SMB. It does not work for FAT32 and exFAT file systems.
MANAGING FILES AND PLACEHOLDERS
All files and subfolders are seen in a file manager with the availability attributes and context menu items mentioned below.
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File is set to be automatically synced. If this is the status of a subdirectory, all files inside it will be automatically downloaded. If a new file is created in such a subdirectory, it gets this status. IF the file is deleted from the disk on remote Agents, the file is placed to the Archive. Unchecking this state through the context menu reverts the file to |
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File version is downloaded to the current device and is available here. It also means that if this file changes on remote Agent, it gets cleared off and reverted to a dehydrated file (placeholder), the file version is NOT placed to the Archive. Local file changes will be synced to remote Agents. Newly created files in a selective sync subdirectory have this status. |
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Dehydrated file - file is an empty placeholder and can be downloaded from remote Agent. It consumes only 1 KB of storage (filesystem header). If the file is updated or deleted on a remote Agent, the dehydrated file is NOT placed to the Archive. If a dehydrated file is copied (using Explorer or CMD), both - the source file and its copy - are reverted to state If a dehydrated file is moved to a different directory, using Explorer it will appear in |
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File is being downloaded and opened in an application. Cancelling download depends how file was selected for download: - by checking "Always keep on the device". To cancel this, click on the menu again and uncheck the option. - by checking "Always keep on the device" for the parent subdirectory. Right-click on the file and uncheck "Always keep on the device". |
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File is being processed in any way: is going to be downloaded or cleared off, local changes to the files are being processed, newly created file is being processed, for example, is being copied into sync folder. Files which are ignored by ignore rules are also marked with this status. |
state. If unchecked for a subfolder, all synced files inside it are also reverted to 
Files can be managed through an application, or a file manager using context menu:
- Always keep on the device. Makes file always available on the device and automatically download any file updates from remote Agents. This menu item may fail to work if there's a non-Windows Agent in the mesh and synchronization of NTFS permissions is enabled through the Profile. Also, a false positive error "Cannot finish file download - problem moving it to its location" may appear if a small file is attempted to be downloaded right after appearing in TSS folder; the file shall be downloaded automatically a few seconds later.
- Free up space. Converts the file to a placeholder. The file is not moved to recycle bin! Until it's processed, file's status is 
and then changes to 
Available when online. If “Free up space” is performed on a subdirectory, all items inside it are cleared but browsing inside it is still possible. The file won't free up space if it's still opened in an application and will keep showing . The file also won't be dehydrated until it's uploaded to one of the configured main servers, read more about it here.
Files free up space if the cleanup timeout is configured in the Agent profile, but do that only when the folder is rescanned periodically or manually. Files with the status "Always available on this device" are not cleaned up.
Double-clicking on a file. If the file is a placeholder, it will be downloaded and opened in an application. The file becomes "Available on this device". Downloading may be delayed by up to 60 seconds (a peculiarity of CloudAPI).
System’s “Delete” deletes files to Recycle Bin and propagates this deletion to remote Agents and puts files in the Archive there.
It does not revert files to placeholders! Additionally, placeholders (with the status "Available when online") will not be even moved to Recycle bin locally.
When the job is removed, all placeholders are removed from the disk from "selective sync" Agents. Hydrated files remain.
TRANSPARENT SELECTIVE SYNC AND 'LEGACY' SELECTIVE SYNC
Legacy Selective Sync is compatible with Transparent Selective Sync enabled on other agents.
NETWORK SHARES
A folder with enabled Transparent selective sync is available over SMB and files are accessible, but with some limitations:
- Placeholders will be created in the TSS share and the user can download files by double-clicking on them, but there will be no context menu for placeholders.
- If the File is not available for download and gives an error shortly after job creation until the Agent fully scans the folder for the first time.
The Agent cannot create a Transparent selective sync folder on a network share. TSS folder must be local.
PECULIARITIES AND LIMITATIONS
- Changed file attributes (timestamps, permissions) are not synced from a placeholder to remote Agents until the file is downloaded locally. For changes to be propagated to remote Agents, attributes must be changed after you download the file. Otherwise, changes will be rewritten as you download the file.
- Renaming or moving of dehydrated files (placeholders) see above. For remote Agents to be able to process rename, they shall have Archive enabled. Be sure that: there is at least one Agent with the full file copy in the mesh before renaming or moving placeholders and lazy indexing is disabled.
- The Archive does not store file versions. Only the files deleted on remote Agents are moved to the Archive in a TSS folder.
- Due to Archive limitations, file edit collision detection does not work on TSS shares on a Windows Agent.
- It's not possible to use new Selective Sync for root of a mounted network share (Z:\foo), Agent will give an error 
Other Errors related to Transparent Selective Sync are mentioned here.
- TSS folder inherits attributes from a previous job or an application that uses this technology (Cloud API). In other words, if an attribute was set on a folder (Always available on this device, Available on this device, or Available when online) when a job is being created, the agent won't overwrite them and will follow those attributes. This may result in unexpected behavior, for example, the files might be synced automatically. Check the existing flags using an elevated Command Prompt with the command attrib. Read more about it here.
- false positive error "Cannot finish file download - problem moving it to its location" may appear if a small file is attempted to be downloaded right after appearing in TSS folder; the file shall be downloaded automatically a few seconds later.
