NFS slow performance, iSCSI working fast

Hi all,

I'm working with sun ZFS 7320, with NFS shares only. All shares mounted to ESXi VMs (running on a blade system). Recently we performed some test and found out the we receiving very poor write speed (900kb - 16Mb at max), checked network load, VM load, any other bottleneck, however we find out that everything working properly. We tried to mount the share to another physical machine, however nothing changed, we still get poor performance.

As a second step we decided to create iSCSI lun and map it to the same servers, the result was magically increased (120Mb - 1.2Gb write speed). Its running on the same network devices, same VLAN (seperated from others).