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Showing posts from May, 2012

Fixing slow NFS performance between VMware and Windows 2008 R2

I've seen hundreds of reports of slow NFS performance between VMware ESX/ESXi and Windows Server 2008 (with or without R2) out there on the internet, mixed in with a few reports of it performing fabulously.
We use the storage on our big Windows file servers periodically for one-off dev/test VMware virutal machines, and have  been struggling with this quite a bit recently. It used to be fast. Now it was very slow, like less than 3 MB/s for a copy of a VMDK. It made no sense.
We chased a lot of ideas. Started with the Windows and WMware logs of course, but nothing significant showed up. The Windows Server performance counters showed low CPU utilization and queue depth, low disk queue depth, less than 1 ms average IO service time, and a paltry 30 Mbps network utilization on bonded GbE links.
So where was the bottleneck? I ran across this Microsoft article about slow NFS performance when user name mapping wasn't set up, but it only seemed to apply to Windows 2003. Surely the patch me…