We have a NetApp Storage system presenting LUNs to a few Hyper-V clusters. When running a system performance trace (in perfmon) on a 2008 R2 there's a warning about a "high level of Split I/O". Reading up on split I/O I find that this is most likely caused by a fragmented drive.
I find it hard to believe that the drive is fragmented in the traditional sense, because everything is virtual (virtual hard disk on a LUN, on a volume, in an aggregate, on a storage system that writes anywhere it sees fit and de-duplicates that data also). So should I even be worried about this? I can't see any evidence of storage problems, such as excessive latency.
Incidentally, running a defrag analysis on one of our VMs shows ~50% fragmented data. I think I read somewhere that windows would automatically split I/O if it detected fragmentation above 20% is that true? The defrag task is disabled, so how would it know?