RAID stripe size

[Edgar Fuß <ef%math.uni-bonn.de@localhost>]

Just in case: What this really is about is chosing the RAID stripe unit size.
On a three-component RAID 5, I think I basically have two options: make a 
stripe the size of a fragment or make it the size of a block.
The data on the RAID set is a Borg backup, and I can examine data on another 
backup server. Since backups are mostly written to, I think I need to 
optimize for write speed.