We tested iSCSI servers by installing and configuring them, putting them through a series of typical tasks, and running performance tests.

Our test bed was based on a dedicated data network provided by an Enterasys C2G124-48 Gigabit Ethernet switch, along with a dedicated control network using another Enterasys switch C2G124-48 switch. The two networks were connected to each other and to our production lab network using a Nokia firewall.

Each iSCSI SAN server was connected directly to the Enterasys network using as many Ethernet ports provided by the vendor with each server. If it was possible to separate control and data traffic, we did so by connecting the control ports to our control network. In some cases, it wasn't possible to separate out the control and data networks, so we ran both control and data over the same network.

Many storage servers support "jumbo" datagrams, a non-standard extension to Ethernet that allows for larger Ethernet frames (up to 9000 octets is common). Depending on the device, this can increase total system throughput by reducing overhead used for packet headers and per-packet processing. The Enterasys switch supported "jumbograms," so we turned on jumbograms for every server that supported it.

Another performance enhancement often used is link aggregation (sometimes called "bonding" or "teaming"), which combines multiple Ethernet ports into a single virtual port that can accommodate the throughput of the component ports and provide high availability. Where link aggregation was supported, we made use of it.

In some cases, we had to configure link aggregation manually on the Enterasys switch; in others, the storage server supported the link-aggregation control protocol (LACP) which automatically brought the ports together. In that case, we simply verified that the Enterasys switch and device agreed on the link aggregation configuration.

We attached four identical servers to the data network, each with a single dedicated 1Gbps connection. Each server also had a 100Mbps connection to the control network. We used an Avocent AMX5100 KVM to control the servers. The servers were all dual-Xeon systems with 3.0GHz CPUs and at least 2GB of memory. Each booted from a locally attached SCSI drive.