Write performance becomes optimized if you involve concatenations across controllers. Volumes are typically at the multi GB level. The difference here is that the OS buffers writes to 'dsk' for efficiency. With rdsk, every character is written immediately to disk. This limitation is overcome with the directio mount option for UFS filesystems.
Every device has a block and character mode.
Prepare volume as a filesystem. Highly acelerated mirror resynchronization after a crash. VM log file that tracks data changes made to mirrored volumes. This will take some time. Write time is significantly longer.