I'm using ARJ compressor under GNU/Linux system to backup mostly FS with a size of 600 GBs aprox., and very large number of files. I'm not using compression, only store with split of 50GB volumes.
So, when ARJ start, it spend so much time to create the first file of volumes. Then additional volumes are copied with "normal" speed.
There is any option to start inmediatly with the first volume. I'm using this parameters:
arj a -jyk -i -r -m0 -vw50000000k <arj_file> <base_directory>