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

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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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