Hi all, we have new Dell Servers with Dell's VMware ESX 6.5 installed. They have multiple 10GB interfaces. With NFS we get expected speed, basically to flood the disks up to their limits. However, with iSCSI the network becomes the bottleneck, we only reach 20% of the possible performance. We installed Ubuntu 16.04 on one of the servers, for testing. With Ubuntu we are able to run iSCSI properly. We tried iSCSI with ESX against a Powerfault MD3860i and against a Synology NAS, both setups show the same slowness. So there must be something wrong with the ESX setup in this environment, I believe. So far we looked at "Best practise guides" for VMWare and tried to play with Jumbo frames, made sure they are enabled (size 9000 as recommended in these guides) on all components and disabled flowcontrol. It did not help. My colleague exhausted all options he can think of, I cannot think of anything either, and we asked VMware but did not have a good answer yet.. Of course it is urgent;-) So I wonder whether I can pick your brains. Do you have any ideas what could cause the issue? Thank you for all ideas Peter