If you notice that the Internet Information Services' (IIS) application pools related to CentreStack are consuming large amounts of RAM nearing the server's capacity, there are a couple of things that you can do to try to remedy this before you consider scaling up (with additional resources/hardware to your existing server) or out (with additional worker nodes to your CentreStack farm).
The first consideration is that due to the fact that file preview generation is an expensive process for large files, you should only generate file preview images for relatively small files if you are having memory issues. Under the Cluster Control Panel -> Settings, you should decrease the maximum file size for the setting labeled: "Don't show file icon preview if file size is larger than." Try setting this figure to half of a Megabyte (500KB) from the default 5MB (5000MB) and see if it helps.
The second optimization is to set the UploadDownloadProxy application pool in IIS to recycle itself if it reaches a certain size. If you decide to do this, please do not cap the Virtual Memory usage. Instead, set the Private Memory usage, and make sure that the figure that you use is large enough to fix your memory issues with the least amount of recycles.
Furthermore, in order to prevent CentreStack's storage component from going down completely as a result of the automated recycles, you will also need to configure the Rapid-Fail Protection's Maximum Failures under the UploadDownloadProxy application pools' advanced settings. Set this figure to a relatively large number, such as 50.
For more information about Memory tuning on the MSDN website, please visit: https://msdn.microsoft.com/en-us/library/ff647813.aspx#scalenetchapt17_topic9