High Priority

If checked, ZipStream's background compression will operate at a higher 
priority. Using this mode may reduce the overall performance of your 
system, but will ensure that files are compressed quickly. 

By default the background compression system will operate at low or 
background priority and will have very little effect on overall system 
performance. However, in some situations this may lead to a large number 
of outstanding compression operations being queued. 

Note:  ZipStream uses automatic measurers to limit the number of 
outstanding compression operations.