What could be tweaked inside the SdFat in order to increase its performance provided I have got a "large" ram available (ie 16kB with 1284p)?
Try browsing this
http://forum.arduino.cc/index.php?topic=180769.0
fat16lib has done some amazing stuff with sdfat on a 1284.
What could be tweaked inside the SdFat in order to increase its performance provided I have got a "large" ram available (ie 16kB with 1284p)?
I need details about your application. Read or write? What performance measure, latency, average transfer rate? What size transfers are you doing? Include as much detail as possible.
SD cards vary greatly you need to select the right one for your app. See this for general info https://wiki.linaro.org/WorkingGroups/KernelArchived/Projects/FlashCardSurvey.