Debugging newnfs

[Daniel Mayfield]

I have a very strange problem between an NFS server running FreeBSD 10 w/ ZFS and a number of FreeBSD 10 VMs running on a XenServer 6.2 SP1 host.  The problem manifests as seemingly random permissions issues and/or IO errors on the clients when the ZFS pool is busy.  There are no entries in dmesg on either side, and no errors logged in nfsstat either.  If I keep the traffic down, the errors subside, but not completely.  Other than tcpdump, how can I go about debugging this?

Dan