Hi lzhao2013,
Further I've noticed is that when I using multi-threads to VixDiskLib_Read(), there is a higher chance to get the VIX_E_HOST_NETWORK_CONN_REFUSED error, although I'm following the Multithreading Considerations.
Very good - so if we assume that your implementation of the threading considerations is correct another restriction with respect to the NBD and NBDSSL transport modes comes to my mind. Please check section NFC Session Limits and make sure that you are not sharing connections accross disks.
I'll try to go through some logs and share more info if I got something interesting.
Also when investigating the logs check whether the server complains about shared NFC connections. Be aware of the fact the limits only apply to NFC connections, i.e. NBD and NBDSSL transport modes.
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Thomas G.