Raw devices vs. File systems for On-Line 5.0

Hi, Recently while I was looking through the Sybase newsgroup, I came across many postings related to the above topic. In particular, Since I am also using Informix 5.0 It seems like a good place for posting my question. Question: I have an ascii data file with 53 fields in it. Each row is composed of 450 characters and there are about 400,000 records in the file. To load the file using dbload into a table with 53 columns, it takes the database approximately 100 rows per second with nothing else running on the machine. However, If I was to split the table into three smaller tables and then load the file into the three separate tables, it takes over 40 hours. So, why the extra overhead. Would it be faster if I do the load into a file system as opposed to a raw device. In addition, when I tried to populate only one of the smaller tables at a time, it took an average of only 1 record per second being loaded. At this rate, it would had taken over two weeks to get it done.! Any guesses??! Thankx Ali