"So does this mean we should not get any disk crossings if the i/o is below 64KB assuming the offset is correct?"  Depends on 2 things:  1) Alignment of partition on the physical device - an issue with Intel-based systems using the old int16 method - which was pretty much every OS until Windows Server 2008, which aligns partitions automatically. The BPG link given in the previous post gives instructions for adapting to misaligning OSes.  2) Alignment of actual physical requests due to file headers, filesystem block size, filesystem metadata, and IO size  If either of these causes an IO to straddle the 64 KB stripe element, you get a crossing, So, we could have an aligned paritition, a filesystem using 4 KB blocks but serving an application which reads a 4 KB header then requests 16 KB IO from the file. Some of those could straddle.
As I understand it the difference is  Disk striping -  When there is Write/ Read of 64KB this will be read or written from another disk as the Clariion uses a element size of 128 (64KB)  Disk crossing -  if the alignment offset is not correctly set ie: multiples of 64KB, then reads/writes will produce disk crossing.  So does this mean we should not get any disk crossings if the i/o is below 64KB assuming the offset is correct?
Disk striping / Disk Crossing