Overview of iSCSI TLV
iSCSI is an IP-based storage networking standard for linking data storage facilities. IP and Small Computer System Interface over IP (iSCSI) storage refers to block access of storage disks across devices connected using traditional Ethernet and TCP/IP networks. iSCSI protocol enables the transport of Small Computers Systems Interface (SCSI) commands over TCP/IP networks. By transmitting SCSI commands over IP networks, iSCSI facilitates block-level transfers over the Internet.
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Priority Flow Control—Priority Flow Control enables eight virtual queues on a single wire and helps send pause frames to a single type of traffic instead of all the traffic on the wire. This feature helps prevent head-of-the-line blocking while maintaining lossless capabilities. In consolidated networks, where a mix of traffic is sent on the same wire, PFC helps prioritize the traffic and assign it to either the drop or no-drop class. PFC is useful for iSCSI networks when they are designed for lossless, oversubscribed networks.
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Enhanced Transmission Selection (ETS)—ETS provides the capability to allocate bandwidth to each traffic class on the same wire. ETS also helps prioritize and optimize the throughput for iSCSI and IP storage traffic, both of which shares a medium with the other traffic on the same link. The guaranteed bandwidth also aids in performance calculations to tune applications during peak traffic.
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Data Center Bridging eXchange (DCBX) protocol—DCBX protocol is used to exchange all the DCB features across the devices and maintain consistency. DCBX protocol helps ensure consistent quality-of-service (QoS) parameters across the network and servers. The features are advertised to the servers in type-length-value (TLV) format using the Link Layer Discovery Protocol (LLDP). iSCSI TLV can be used to separate iSCSI traffic from other traffic. It can also be used to extend lossless behavior to the Ethernet infrastructure.
The iSCSI TLV over Data Center Bridging eXchange (DCBX) protocol feature lowers the cost of the lossless Ethernet deployment solution. iSCSI targets that can perform end-to-end iSCSI with initiators, are present.
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The adapter management application must ensure that the Willing mode is set to Enable in order to accept the CoS values from the switch. |
Guidelines and Limitations
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We recommend that you use iSCSI TLV-supported CNA on both, the host and the target.
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We recommend that you use CoS 4 for iSCSI traffic and create a custom 6e QoS policy based on the default-nq-6e-policy template, since most of the CNAs use CoS 4 for iSCSI.