Cached Exchange Mode in a Remote Desktop Server Environmentaugust 2010

Cached Exchange Mode in a Remote Desktop Server EnvironmentAugust 2010

Cached Exchange Mode in a Remote Desktop Session Host environment: planning considerations

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Cached Exchange Mode in a Remote Desktop Server EnvironmentAugust 2010

Contents

Introduction

Storage footprint

Performance impact

Networked storage

Conclusion

Cached Exchange Mode in a Remote Desktop Server EnvironmentAugust 2010

Introduction

This document is provided as an addendum to the documentRemote Desktop Session Host Capacity Planning in Windows Server2008R2( and is provided so that you can accurately evaluate Outlook Cached Exchange Mode when you prepare to deploy Microsoft Office2010 in your Remote Desktop Session Host (RDSH) environment. The Remote Desktop Session Host Capacity Planning in Windows Server2008R2document should be the starting point for any analysis of anRDSH deployment.We generated the disk and network I/O statistics that are shown in this document by using the same environment and test procedure that is described in the “Knowledge Worker v2” scenario in the Remote Desktop Session Host Capacity Planning in Windows Server2008R2 ( article.

Historically,MicrosoftOutlook has only been supported in anRDSH environment when it is deployed in Online Mode and connected to a Microsoft Exchange Server.This is still the recommended configuration for Microsoft Outlook2010 when it is deployed in an RDSH environment. However, customers who deploy Outlook2010 now have the supported option of enabling Cached Exchange Mode when Outlook2010 is installed in a Remote Desktop environment.Cached Exchange Mode might be ideal for deployments in which Outlook is connecting over a high latency connection to an Exchange server that is located remotely. For the relatively few users who access Outlook through a remote desktop, this might be the ideal configuration. However, Online Mode against the Exchange server is still the most scalable and optimized configuration for large deployments.

This white paper coversthree major areas that you should consider when you deploy Outlook2010with Cached Exchange Mode in a Remote Desktop environment:

Storage footprint
Performance impact
Networked Storage

Storage footprint

In Cached Exchange Mode, Outlook stores a local copy of each Exchange mailbox and address book on disk.Since no data is stored locally in Online Mode, Cached Exchange Mode increases the storage that is required for an Outlook2010 deployment proportionally to the size of each deployed Exchange mailbox.The following example demonstrates that increase.

Exchange mailbox + Outlook Address Booksize / Local Disk Footprint (Cached Exchange Mode) / Local Disk Footprint (Online Mode)
~500MB / ~1 GB or more / ~0 MB

Performance impact

Due to the changes in disk and network load, deploying Outlook2010 in Cached Exchange Mode impacts the number of users who can be supported on a single RDSH instance.

Using the same test that is described in the document Remote Desktop Session Host Capacity Planning in Windows Server2008R2 ( for Knowledge Worker v2, we measured the disk and network I/O characteristics in an RDSH environment.The following chart describes the disk I/O behavior of Outlook2010 in Cached Exchange Mode.

We took this measurement after the initial mailbox sync was completed. It is the Outlook2010 behavior in “steady state” usage. Expect I/O loads to be heavier during the initial mailbox sync. Because Online Mode does not store a local copy of the mailbox, there is essentially no steady state disk I/O in that configuration.

Networked storage

In many RDSH and Virtual Desktop Interface (VDI) environments, disk storage is located on a separate networked location from the primary server.This is advantageous in Pooled VDI infrastructures, because it does not require a rebuild of the Outlook data file (.ost) each time the user logs in from a new endpoint.

With Outlook2010 in Cached Exchange Mode, the data store is accessed over the network rather thanfrom a local hard disk.This scenario is only designed for networks that have high bandwidth and high levels of reliability.Keep in mind that this scenario causes all Outlook Disk I/O to be directed over the network.

The following chart shows the differences in network I/O load, based on the storage location.The red line represents the total load when the .ost file is placed on a remote location (SMB network share).Network load increases substantially when storage is located in a remote location.In our specific test, the average network load increased by a factor of approximately 10, when compared to a locally stored .ost file.This scenario is only recommended in configurations that can sustain this I/O load. Otherwise, users’ Outlook user experience might be degraded.We strongly advise that you test this configuration in a test environment that closely mirrors your deployed environment so you can validate that Outlook client performance and user experience remain acceptable, evenwith the elevated network loads.

Conclusion

The information in this document, and the information that is contained in the overall RDSH scalability documentationshould provide you a good starting point to evaluate and test Outlook2010 with Cached Exchange Mode in anRDSH environment.As with any new configuration, it is important that a deployment in this configuration be dependent on extensive testing in a test environment that closely mirrors yourreal-world environment.