12GB isn't really a lot for a SQL Server. Especially if you have SSAS, SSIS and SSRS all on the same instance. YOu also say you have RAM ring fenced for SSAS, Is this in addition to the remaining 4GB? If not SSAS is really going to struggle as it needs to share those 4GB with SSRS, SSIS, the OS (probably going to be using at least 2GB), and anything else running on the server. Is the Server not expected to be doing much most of the time? Is slow calculation time acceptable?
Out of interest, what licence are you running, Standard, BI or Enterprise?
Excuse my typos and sometimes awful grammar. My fingers work faster than my brain does :-P
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