virtio_scsi performance

Hi everyone, I've been having a performance issue with virtio-scsi for some time after migrating from ESX last year, with the VM becoming unresponsive and sometimes causing other VMs using virtio-scsi to hang too. I previously only saw the issue with Windows VMs during Windows updates, usually...

Can anybody explain the big performance difference between VIRTIO SCSI and VIRTIO SCSI single especially when using iotread=0 and iothread=1? read : io=1637.7MB, bw=39596KB/s, iops=6491, runt= 42350msec VIRTIO SCSI iotread=0 read : io=1637.7MB, bw=41136KB/s, iops=6744, runt= 40765msec VIRTIO...