we are aiming to extend the disk space of our Marklogic 8 Database to 35TB, I wonder if there is any limitation for max disk space for Marklogic 8?
MarkLogic will support Petabytes of data, so 35 TB is not a problem, assuming you have enough computing power and RAM to support the number of forests that you have. Although it depends greatly on your individual application, a general rule of thumb is 2 threads (or vCores) per forest, and 4Gb RAM per thread/vCore.