Description

It is possible to use Virtual Vault with Outlook in a purely "online mode" (non cached) and reduce the disk usage of Vault Cache.

In order to use this type of configuration, the Enterprise Vault desktop policy can be setup and modified with the following settings:

1. Go to the Enterprise Vault Admin Console (VAC).
2. Go to Directory on..| EV server name | Policies| Desktop Policy.
3. Right click Desktop policy go to properties.
4. Go to Advanced tab
5. Select Drop for Vault Cache and select Offline Store Required and set to NO.

6. Go to the Vault Cache TAB and Under List size of Vault cache, choose the drop down and select Do not store any items in cache.

With Outlook in "online mode" Virtual Vault and archived messages will be accessible.

What is happening in this configuration is that only the meta data cache (MDC or header information) is synchronized and held locally in an MDC file, which can take up minimal space.  When an end user views an archived message or previews a message in Virtual Vault, as the item is not in the users Content Cache, the item has to be downloaded into the users windows profile temporary location, where it is opened to the user. 

Any files that are opened in this way remain in the users temporary location until Outlook is restarted, so if a user previews the same message twice there if only one download, unless outlook is restarted.

To reduce the load of the Outlook Preview Pane unnecessarily recalling an archived item, a couple of things can be done to help to mitigate this.

1. Change the Enterprise Vault Desktop Policy | Advanced tab | Virtual Vault settings | "Show content in Reading Pane" to not be any other option except "Always show content". 
2. Also to disable the use of the Outlook Preview Pane".

Note: This configuration may save on disk space at the end users machine, however, the cost for this configuration is increased network activity as users preview or open archived items as they will have to be downloaded from the Enterprise Vault server, due to them not being held locally in the Virtual Vault Content Cache.

Additionally, MDC / Metadata cache can be large, regardless the configuration of "not to store any content locally", as it provides the visible structure to Virtual Vault, so you will always get a full MDC file for each archive you have opted to synchronize.