Increased RAM, Worse Performance Setup:


Windows Server 2008 R2 
SQL Server 2008 R2 SP1
240GB RAM
TempDB is 8x16GB data files w/out auto-grow (128GB total)
Physical/Stand-alone Server


This server is used for ETL processing. We just installed more RAM in this server for a total of 240GB RAM. SQL Server services are the only real things running.

The memory shows up fine in the BIOS, OpenManage and Windows.

If I configure SQL Server to use a Min/Max of 70/100GB memory, we have no issues. However, once I increase that to 120/150GB, I get the following error when I run one of our ETL processes:


  Could not allocate space for object '&lt;temporary system object:
  422234507706368&gt;' in database 'tempdb' because the 'PRIMARY'
  filegroup is full. Create disk space by deleting unneeded files,
  dropping objects in the filegroup, adding additional files to the
  filegroup, or setting autogrowth on for existing files in the
  filegroup. (Msg 1105, State 2, Procedure Unknown, Line 1)


We have never run into this issue prior to changing the memory configuration. After re-configuring back to the original 70/100GB, we do not receive this error.

Things I've tried:


Set the TempDB data files to auto-grow. This simply results in the files auto-growing until disk-capacity is reached and then fails.
Add more TempDB data files. Same error as shown.
Increase the TempDB size to 8x32GB (256GB total)


I'm at a loss as to what could be causing this problem.
Thanks to everyone for your help.

After pouring through some execution plans, it turns out there is a JOIN that is being processed differently based on the amount of RAM available. With less RAM it evaluates it with a Hash; with more RAM, it uses a series of Merge Joins. 

So basically it came down to poorly written T-SQL, which I am presently refactoring.