The iSCSI connection is closed by the iSCSI target and the connection closed by peer refers to TCP session reset/closure that is sent from the target storage to the ESXi host.
A network error occurred while the client was receiving data from the server.
This issue occurs due to improper storage array configuration, host networking configuration, or the VMware ESXi product. The server accepts the connection, processes the request, and sends a reply to the client.
When the server closes the socket, the client believes that the connection has been terminated abnormally because the socket implementation sends a TCP reset segment telling the client to throw away the data and report an error.
Over-saturation of the SAN or SAN array, resulting in loss of communication, or storage task completion after the ESXi host has already stopped the task due to timeout (5000 ms).
Duplicate SAN targets IP addresses, resulting in intermittent connection loss and other anomalous behavior.
SAN target connection load balancing. Disable connection load balancing when using VMware ESXi software iSCSI initiators. You can utilize the Round-Robin multipathing policy to configure load balancing.
VMkernel networking misconfiguration:
When using multiple VMkernel ports for software iSCSI, ensure that the number of VMkernel ports is lesser than or equal to the number of physical network interfaces.