Welcome to the ITFreeTraining video on Offline Files. Offline Files was originally designed
to allow users to access their files when the server was not available. Nowadays it
still performs that function but also works with a lot of other Windows technology to
provide the user with a better experience. In this video I will look at how Offline Files
works and how it works with other Windows Technology.
Offline Files was first introduced in Windows 2000. It is also referred to as client side-caching.
Let’s consider a file share with files in it. The user is able to decide which files
to make available offline. Once these files have been made available offline, and if the
network was disconnected, the user is able to access their files from the local cache.
Changes to the files are automatically synced back to the server when it becomes available.
This is basically how Offline Files works; however, since it was first introduced it
has been improved and additional features added.
Most of the major changes happened in Windows Vista, although there have been improvements
made after this. Sync Center works in the background to sync files. Before this, synchronization
could be configured to happen when the user logged in, logged out or the network became
available. The process was not completely transparent. Sync Center makes the process
transparent to the user, syncing the files in the background, and Offline Files automatically
performs synchronization between locally stored files and network stored files as required.
The next feature is slow link mode. If this is enabled using group policy, offline files
can automatically change to the local copy when a slow network connection is detected.
Sync Center can also be configured to sync files over a slow network connection.
The next feature is transparent caching. This can be enabled by the administrator using
group policy. When enabled, a file that is accessed over the network will be stored in
the local cache. When the user attempts to access the file a second time, a quick check
is done to the network share to ensure the file has not changed, if the file has not
changed the local copy of the file is used rather than copying the file across the network
a second time.
This works well with BranchCache. When BranchCache is enabled, transparent caching can retrieve
the file from the local network using BranchCache rather than copying it across the network.
Offline files also allows the offline cache to be encrypted using EFS. This prevents the
files from being read by a 3rd party if the computer holding the files is lost or stolen.
The last feature that I will look at is a feature that had been added to Windows Server
2012 R2 and Windows 8.1. This is Always Available Offline Mode. When in this mode, Windows will
always use the offline cache even when the network is available. I will now have a close
look at some of the features of offline files.
Sync Center controls the synchronization process. It is a bi-directional syncing process. This
means changes can occur on both sides. In a lot of cases this works quite well. For
example, if a user takes their laptop home and makes some changes, when they return to
work the changes will be synced to the network. While at work, changes will be made to the
network copy and then transferred to the local copy. In this case, it is unlikely the user
will change the same file on the network and local copy at the same time. However, if this
were to occur, this would result in a conflict. More on that in a moment.
To open Sync Center, go to the sys tray and select the icon Sync Center. If the icon is
not present press the up arrow to access additional icons. Once I select the icon, Sync Center
will open.
Currently Sync Center is configured to Sync offline files. If a file was changed on the
local cache and network at the same time, this is known as a conflict. When this occurs,
Sync center will prompt the user to determine which version they want to keep or if they
want to keep both versions.
If I select the option “View sync conflicts”, this will show any conflicts that currently
exist. There are none at present. The next option “View sync results” will show the
result of the last synchronization. This process will happen in the background and should be
transparent to the user, but it is possible to manually start the sync process.
The next option allows additional sync partnerships to be setup. For example, you could set up
a partnership with a compatible mobile device.
The last option is “Manage offline files”. This contains all the options for offline
files. In the next video I will have a look at these options.
The next option that I will look at is transparent caching. Transparent caching is not part of
offline files. However, it can be used with offline files or as an alternative to offline
files. To understand how transparent caching works, consider that you have a file share.
This file share contains a public share that is too large to be made available offline.
A remote user connects up to this sever - however, they connect to it over a slow link. Offline
Files can be used to make certain files available offline. However, in this case, if a large
amount of files were made available offline using Offline Files, the computer would be
attempting to sync all these large files over a slow network. Not the most ideal solution.
You can start to see why some thought may be required to determine what files you should
and should not make available offline. The situation is also complicated in that there
may be a large amount of files on the file server making it difficult to determine which
files should be made offline. Perhaps the user does not know themselves ahead of time
which files they may need.
In order to improve performance over a slow link like this, transparent caching can be
used. It works simply like this. If the user was to request a file from the file server
it will be copied over the network.
If transparent caching is enabled through group policy, a copy of the file will be stored
on the local computer in transparent cache. So transparent cache simply stores remote
files in a local cache, the user can then access the local copy rather than the remote
copy. However, it is possible that the file was changed since it was copied over to
the network and the user could be accessing an outdated copy.
To solve this problem, the computer will check with the file server to see if the file has
changed. The server will response back. In this case, the file has not changed and the
transparent cache will still be used. This prevents the user from using a file that is
out of date.
If the other case occurs, the computer asks if the file has changed and the server responds
back that the file has changed. The old file is discarded, and a new copy of the file is
transferred over the network for the user to use and also copied to the transparent
cache.
So what occurs if the server is not available, either the server is down or the network is
down? When this occurs, the transparent cache will not be available. With offline files
a file is available to the user when the server is not available, that is the idea. However,
this is not the case with transparent files. You can see that transparent files can work
with offline files to give the user a better experience, but is not a replacement for offline
files.
The next feature that I will look at is BranchCache. Branch Cache works with offline files. If
you are not sure how BranchCache works, well it works like this. Once again you have a
file server on a remote network. Our user is on another network that is separated by
a slow network connection.
In order to use BranchCache, it needs to be configured on the remote network, in this
case on one of the servers. Now consider that a different user on the network opens a file
on the remote file share. The file would be transferred to the user using BranchCache;
however, a copy would also be kept on the BranchCache server.
Now when the user opens the same file, the file is transferred from the BranchCache server
rather than across the slow network connection a second time. Just like Transparent Caching,
BranchCache does a check with the remote server to make sure the file has not changed before
it is transferred. Just like Transparent caching, the files are not available during an outage.
Even if the BranchCache server is available and the file is in its cache, it will not
transfer the file to the user unless it can check with the remote server to make sure
that the file has not been modified. So once again, a technology that works with offline
files but is not a replacement for offline files.
The last feature that I will look at is Always Offline Mode. When Offline Files is being
used and this option is enabled, the user will always use the offline copy even when
the server is available in good network conditions.
Consider that you have a file share and on that file share are some files. The user may
be a remote user or even on the same network as the server so there may not be poor network
connections between the two. It may seem strange that an administrator would want to configure
it this way, but if you consider the user is using large video files or they are connected
on a network connection that charges based on how much data is transferred, you can see
why some administrators may enable this option.
If Offline Files is configured, sync will copy the files that are configured to be made
available offline to the offline cache on the local computer. Once this is done, when
the user opens a file stored in the offline files cache, it will be retrieved from the
local cache rather than the file server.
The point to remember here is that Offline Files does not check for file changes like
Transparent Cache and BranchCache did. When changes are made to a file, the changes will
be uploaded to the server using the normal sync process.
Always Offline Mode is only available in Windows 8 and Windows Server 2012 and above. To configure
it, slow-link needs to be configured to a latency of 1 millisecond using group policy.
In the next video I will have a look at how to do this. If this setting is configured
on earlier operating systems, the operating system may change between offline and online
rather than using only the offline copy only.
That covers the basics of how offline files and some of the other technology work in Windows
to make file access faster. In the next video, I will look at how to use these features in
the real world to get the best results for your users. Until then, thanks for watching.