Work Directory Usage with Persistence Disabled

[Mitchell Rathbun (BLOOMBERG/ 731 LEX)]

In the documentation, Ignite is described as a pure in-memory solution when 
persistence is disabled. However, even with persistence disabled, I am noticing 
that the Ignite work directory must be set to an existing directory, and that 
this directory has the 'marshaller/' directory created with files written to 
it. Why is this needed if persistence is off? Is there anyway to avoid writing 
to the file system completely?