I have a 10-disk RAIDZ in Solaris 11.1. Its connected by 8G fibre. I have created a ZVOL, made it available with COMSTAR and mounted it on another machine connected by fibre. When I benchmark it with large files, I get ~700MB/s read and ~150MB/s write. That's averaged. Upon closer inspection the read speed is totally steady but the write speed is constantly fluctuating from all the way down from 50MB/s to 400MB/s.
I know ZVOLs use sync writes but should I get this slow write speed and be seeing this fluctuation? I feel like I should get better (or at least consistent) write without having to have a ZIL.