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Exchange and Outlook have been best friends for a very long time—Exchange Server just turned 21, and Outlook has been around nearly that long. Over that time, the way that the two products work together to store email data on the client has evolved to keep pace with improvements in client storage and processing capability. As Microsoft has placed increasing emphasis on Office 365, they’ve rolled out new capabilities and features that depend on both fast, reliable networking and fast, high-capacity storage on the client. These dependencies can be challenging when you need to manage user profiles to improve client performance in physical, virtual, and cloud-based desktops.
Exchange and Outlook storage evolution
The first Exchange clients only worked in online mode; as soon as you disconnected from the network, you couldn’t send, receive, or read mail. Microsoft quickly added the ability to use a personal folders (PST) file to store mail while offline, and PST files quickly became ubiquitous despite the fact that they were easily corrupted and thus prone to data loss. In later versions of Outlook, Microsoft moved away from the PST file with the introduction of the Office storage table (OST) file format, a more robust but slightly less portable replacement for the PST file. They even dabbled with a slimmed-down client-side version of the Exchange Extensible Storage Engine (ESE), codenamed “Rosebud,” but it proved to be far too resource-hungry to be a permanent part of Outlook.
In Outlook 2013, Microsoft introduced the Sync Slider to give users more control over how big their OST files could get. This turned out to be necessary because Exchange 2010, Exchange 2013, and Exchange Online all enabled progressively larger mailboxes to be efficiently managed on the server side. The PST / OST system was designed when a “large” mailbox might be 100MB, but Microsoft steadily raised Exchange Online storage limits from 10GB to 25GB to 2013’s 50GB to the current 100GB limit in Enterprise plans. At the same time, the broad availability of high-speed, low-cost disks enabled on-premises administrators to raise their mailbox size quotas too.
OneDrive storms onto the scene
Exchange Online has famously been described as the “gateway drug to the cloud.” Microsoft has been working hard to convince its customers to adopt other Office 365 workloads too, and OneDrive for Business has been a good example of their success. By some estimates, OneDrive is the second-most-widely-deployed Office 365 workload (behind Exchange Online). The idea behind OneDrive for Business is simple and powerful: keep your files in the cloud, invisibly synced to your devices, so that they’re safe from loss or damage and can easily be shared or accessed whenever you need to. Over time Microsoft has integrated more of its product line with OneDrive, including the Office desktop, mobile, and web apps and Windows 10. The net result is that an increasing number of users are turning to OneDrive for Business to store files that, in the past, would have been on file servers or tucked away in “My Documents.”
Microsoft has added fuel to the OneDrive fire by raising the per-user storage limit to a somewhat ridiculous 1TB per user. Very few users have this much data (if you exclude music, videos, and so on), which is a good thing considering how OneDrive for Business storage works. Unless you’re using the Windows 10 Fall Creators Edition, and have enabled OneDrive Files On-Demand, any folders you’ve chosen to synchronize will be completely synced to a default location in the user’s profile. As long as the user stays on a single machine, this is fine, but it can blow up spectacularly if the user roams… especially in a VDI environment. For that reason, many organizations that use VDI but don’t want to give up the benefits of OneDrive disable the sync client and require users to work through the (very good) OneDrive web interface. This is not an awesome solution but it’s better than forcing users to wait for their profile to resync every single time they log in.
Profile bloat and the cloud
Exchange administrators are used to various problems that arise because of the way OST files work. Each OST file contains a cookie that ties it to a specific Outlook profile on a specific machine. Some kinds of server changes can result in Exchange insisting on a full resynchronization of the OST file, and of course if the user removes the OST (or it’s damaged) a full resync will be required. Because the OST file is stored as part of the user’s roaming profile, this quickly becomes a problem when a user logs into a new machine— having to wait for a multi-gigabyte OST file to synchronize to a new machine is an unwelcome experience—all the more so when the user is using a shared desktop environment and doesn’t realize that their desktop is actually being provided by a virtual environment where their profile has to be synced. This is especially challenging in a non-persistent virtual desktop environment where the entire Outlook cache will try to re-synch on every login.
Microsoft has tried to lessen this problem in several ways. One is with the Sync Slider; another is by improving the quality of cloud archive features in Office 365 (and adjusting pricing to make it more attractive), and a third is improving Exchange search functionality to make it easier to work when the local OST only contains part of the mailbox contents.
On the OneDrive side, most of Microsoft’s efforts have focused on making the sync experience better for roaming clients—for example, OneDrive can detect when it’s on a metered network (such as in-flight wifi), and it allows you to set bandwidth limits for upload and download. The introduction of Files On-Demand means that users can more feasibly work without having to sync every single file in their OneDrive library, but it requires deployment of the latest version of Windows 10—a case where the cure might be worse than the disease.
Taming profile bloat
There are a few proactive steps you can take to help reduce profile bloat:
- You can force all your users to run Outlook in online-only mode. This completely eliminates the use of OST files, but it also means users are completely at the mercy of the network connection between their Outlook instance and their mailbox server. Network problems will quickly become obvious as users see mysterious and transient Outlook errors. This isn’t a great solution for most organizations.
- You can use Group Policy settings to force a value for the Sync Slider across clients. This limits the age of items in user OSTs but doesn’t limit their size. It can also inconvenience users by making it more difficult to work with older items—depending on job role, some users may need access to items older than whatever limit you’ve imposed. Because these settings apply to the user no matter where he or she logs in from, it may also have the undesired side effect of restricting behavior on machines (such as a home desktop) where you don’t care about profile size or sync time.
- You can aggressively implement retention policies to force more mail to an online archive, lowering the size of the OST file. This has the same drawbacks as limiting use of the Sync Slider—if users need older mail, it won’t be available to them without additional traffic to the server.
For OneDrive, the problem of profile bloat is a little more difficult to solve. Administrators don’t have a centralized way to control which folders individual users sync, and most users will happily accept the default of syncing all folders anyway. If you turn off the OneDrive sync client, users can still work with OneDrive files but it’s a more complex process than with the sync client installed, meaning you’ll need to train (or at least explain to) them how to do it. For most enterprises, updating to Windows 10 Fall Creators Edition to get Files On-Demand isn’t going to happen in the next 12 months or so, so that’s not really a helpful option either.
Advanced profile management for the modern cloud
The ideal combination is to give users the full flexibility and power of Microsoft’s tools while still providing good logon and sync performance for users. The best way to accomplish this goal is to adopt modern profile management tools, such as Liquidware’s ProfileUnity. ProfileUnity is a sophisticated User Environment Management toolset that supplements roaming profiles with ProfileDisk, a robust container-based mechanism that allows you to pre-provision Outlook OST files, OneDrive documents, and more in a VHD/VMDK that is seamlessly available to the user no matter where she logs in. With ProfileUnity, you can deliver the full experience that your users expect—fast, reliable profile synchronization that makes their data available when they need it combined with the power of Microsoft’s Outlook and OneDrive suites.