Why does my 10GB iSCSI setup seem see such high latency and how can I fix it?

I have a iscsi server setup with the following configuration
Dell R510
Perc H700 Raid controller
Windows Server 2012 R2
Intel Ethernet X520 10Gb
12 near line SAS drives
I have tried both Starwind and the built in Server 2012 iscsi software but see similar results. I am currently running the latest version of starwinds free
iscsi server.
I have connected it to a HP 8212 10Gb port which is also connected via 10Gb to our vmware servers. I have a dedicated vlan just for iscsi and have enabled
jumbo frames on the vlan.
I frequently see very high latency on my iscsi storage. So much so that it can timeout or hang vmware. I am not sure why. I can run IOmeter and
get some pretty decent results.
I am trying to determine why I see such high latency 100'ms. It doesn't seem to always happen, but several times throughout the day, vmware is complaining
about the latency of the datastore. I have a 10Gb iscsi connection between the servers. I wouldn't expect the disks to be able to max that out. The highest I could see when running IO meter was around 5Gb. I also don't see much load
at all on the iscsi server when I see the high latency. It seems network related, but I am not sure what settings I could check. The 10Gb connect should be plenty as I said and it is no where near maxing that out.
Any thoughts about any configuration changes I could make to my vmware enviroment, network card settings or any ideas on where I can troubleshoot this. I
am not able to find what is causing it. I reference this document and for changes to my iscsi settings
http://en.community.dell.com/techcenter/extras/m/white_papers/20403565.aspx
Thank you for your time.

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