Six iSCSI SANs unleashed

We've all been hearing about the simplicity and low cost of iSCSI for years now -- and how iSCSI would topple FC (Fibre Channel) as the storage networking technology of choice for shops moving from DAS to SAN. Yet entry-level SAN systems, such as those from Dell/EMC and Hewlett-Packard, although quick to adopt low-cost SATA drives, have continued to stick with FC interfaces. Even those that have offered iSCSI typically included FC as well. Fibre Channel has remained king, even for small SAN deployments.

That's finally changing. The current crop of iSCSI storage arrays prove that cost-effective SAN storage is definitely mature, leaving FC arrays comfortable only at the high end. For most small infrastructures, the performance of FC simply isn't necessary, and the cost differential is significant. The combination of SATA hard drives and the iSCSI protocol has finally engendered the new era of storage we've been waiting for, especially for small to midsize infrastructures.

At the true low end of iSCSI SAN implementations, you find that iSCSI-connected servers don't require HBAs to talk to the SAN array -- standard Gigabit Ethernet NICs and software iSCSI initiators will provide connectivity. Standard gigabit switches can then be used to create the SAN itself.

Above the iSCSI software initiators come the iSCSI HBAs that off-load iSCSI processing from the server CPU and handle it in hardware on the HBA itself. Working with Gigabit Ethernet switching that supports jumbo frames, this type of iSCSI connection could push more than 100MBps to and from the iSCSI array. Not too shabby for commodity hardware.

The six products I tested show the current spectrum of iSCSI solutions available on the market today. The Adaptec, Celeros, and Rasilient units represent the lower end in price and functionality, whereas EqualLogic, Intransa, and NetApp bring more enterprise features to their products at additional cost. In addition to providing iSCSI services, these products also present a relatively wide variety of storage features, such as replication, clustering, snapshotting, and supported RAID levels. Adaptec and NetApp even include NFS and CIFS file sharing.

Notably absent is EMC, which expressed interest but ultimately declined to participate. The poor performance turned in by the Dell/EMC AX100i might have something to do with that, but I would have liked to have given the EMC CX300i a run through the lab.

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My evaluation focused on configurability, storage management features, and iSCSI performance. I ran a battery of performance tests under both Linux and Windows, using software initiators as well as iSCSI HBAs from Alacritech and QLogic. I tested throughput and I/O using various block sizes, running random split tests (50/50 reads and writes) as a harsh measure of general-purpose performance and streaming read and write tests to get a feel for maximum raw throughput.