9.3 iSCSI Network Analyzers

Comparable diagnostic analyzers for IP SAN environments are also available, although in the main these products are simply enhancements of traditional IP network analyzers. LAN and WAN protocol analyzers have evolved alongside IP networking, and they let you capture and decode data on virtually any link speed, including 10Gbps Ethernet.

Network analyzers capture and decode link layer and network layer protocols, as well as upper-layer protocols in some products. In this way, you can verify Ethernet MAC layer communications on local segments as well as IP and TCP sessions through the network. The unique addition for iSCSI analysis is the breakout of the iSCSI PDUs that are encapsulated within TCP/IP, as shown in Figure 9-4. In addition to TCP session status, the analyzer display decodes SCSI commands, status, and data so that you can trace both transport and SCSI protocol status.

Figure 9-4. A SNIFFER iSCSI protocol trace (courtesy of Network Associates)

As with Fibre Channel analyzers, IP network analyzers typically include performance statistics so that link utilization can be monitored over time. One of the great unknowns in SAN deployment is the actual bandwidth required for various storage applications. Because part of the value proposition of IP SANs is the ability to use common IP network infrastructure for storage traffic, the ability to accurately provision bandwidth based on sampled utilization is key to optimizing performance and avoiding excessive oversubscription of links.