It’s no secret that organizations that have a native Microsoft Office 365 deployment and non-persistent VDI will experience latencies when using Outlook. This will happen with the full Outlook client, because Outlook uses a cache file for email called an .ost file. The size of the .ost file is often quite large, is always changing, and always being accessed, which complicates matters. When users cannot get their work done, the side effect can be loss of profits when email is the primary source of communication with customers. In the early days of this problem there wasn’t a lot that could be done, but today there are options such as FSLogix Cloud Cache. Let’s discuss!

The Problem with Outlook when used in VDI

We already know that Outlook can perform slowly in VDI virtual machines, and if your organization is like many others, this is unacceptable and must be fixed. However, the real problem is that the OST (aka – Cache Mode) file can’t roam with the user using traditional means like Folder Redirection or Roaming Profiles. We NEED cached Exchange mode when using Office 365 to deliver a good user experience, but there just isn’t a good way to get it to work without considering 3rd party applications.

Alternatively, some companies use the simple work around of deploying a desktop shortcut to Outlook Web App (OWA), but in many cases the full featured product is needed. This can be due to user preference, or plugins that just simply will not work in OWA. So, what can you do if the full Outlook client is required in your VDI deployment?

Profile Management

As mentioned the way to resolve the .ost cache mode problem is to deploy profile management with a 3rd party solution, but not all profile management solutions are created equal. You may find yourself with a profile management solution that cannot cache the Outlook .ost file in a way that is necessary to be successful.

One company that’s worth a look is FSLogix. Their The difference between the products is that while Profile Container encapsulates the entire profile in the VHD container, Office 365 Container focuses only on Office data and is designed to work alongside any existing profile management platforms you might be using. Sounds interesting, right? So, how does FSLogix Office 365 Profile management work?

  • Each user’s Office 365 information will be stored in an Office 365 profile container
  • The storage for the container is presented as a VHD to the virtual machine
  • The VHD allows the virtual machine to see the files it needs access to as local

It’s that simple, and once configured your users will get their full Outlook client with the performance they expect while working. Other companies are doing this as well, but FSLogix is the only company that makes products that work for all Office 365 data types, including SharePoint, OneDrive, Teams, and Skype for Business. Going a step further, FSLogix also supports concurrent access to containers, is profile agnostic, and has a single/multi-user roaming search index. All your bases are covered with this solution.

Improving the User Experience with Cloud Cache

Cloud Cache is a new capability within FSLogix Profile and Office 365 Container that introduces high availability for containers and extends resiliency within the FSLogix toolset. Imagine that your Office 365 connection to Exchange online drops. The user experience would be that Outlook connectivity to real-time data can cease to function. Similar problems would be seen for network interruptions to Office 365 data for other Microsoft cloud offerings as well. So, how can Cloud Cache help here?

Cloud Cache adds two critical elements to your FSLogix deployment:

  1. A truly local copy of any Office 365 (or Profile) data users have accessed – As you access data from your remote container, that data is stored in a local cache. This happens at the block level, so it’s not caching the entire OST file, for example, only the blocks that have been requested. The cache can be configured to build over time, building towards a complete local cache over time, or to clear at logoff. Any desktop (physical, persistent or non-persistent VDI, or RDSH) can benefit from this because it ensures that, should that data be required during an outage, applications continue to function.
  2. The option to have a failover copy of the Office 365 or Profile containers in any location, even the cloud Cloud Cache also includes the ability to store users’ Office 365 or Profile Containers in multiple locations at the same time, even in the cloud via native storage APIs. Cloud Cache will write to all configured locations but will only read from a primary location. If that location becomes unavailable, Cloud Cache connects to another location. When the original location comes back online, Cloud Cache will ensure it is up to date and switch back to using it as the primary. Using native cloud storage APIs saves money when compared to cloud-based SMB storage offerings and being able to place user data in any location on-premises or in the cloud gives you the ability to deliver high availability and disaster recovery without having to deploy expensive or complex hardware-based solutions.

It’s all about your Business Users

Having productive employees ensures that any organization can continue generate revenue as expected. Ensuring Outlook performance for communication with customers is critical, extending your deployment with features that ensure storage continuity, and disaster recovery can support long-term business success.



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FSLogix is a three-time Best of Citrix Synergy award winner, including Best of Show at Citrix Synergy 2018. To learn more about our products and why they’re the best solutions for helping you manage applications, user profiles, and Office 365 data, head over to and take a look around.