Alexey - I am having the exact same problem as you. As a partial solution, I tried using serialize/deserialize (from the FEX) before save. With a ~2.5GB cell array of structures, the command save('blah.mat',serialize(str),'-v7.3') took about a minute, as opposed to a couple of hours with save and v7.3 alone. Unfortunately, for me this only worked with variables of around 2.5GB in size. Trying the same approach with a 8.5GB cell array of structures never quite finished serializing/saving before I got frustrated and Ctrl+C'd it.