Midrange SANs master high-end features

SAN storage systems continue to evolve quickly, with features trickling down from market leaders such as EMC and Hitachi Data Systems to midtier players. The three systems reviewed here, from Compellent, iQstor, and Xiotech, offer a surprising array of functionality including nearly every feature one might find in $250,000 enterprise-class systems except CAS (content addressed storage). Their impressive feature sets include 4Gbps FC (Fibre Channel) connectivity, iSCSI support, tiered storage, local and remote replication and snapshots, and even thin provisioning, boot from SAN, virtualization, and automatic expansion of volumes. Compellent even provides automatic migration of data from first- to second- or third-tier storage -- an ILM (information lifecycle management) tool that is usable without requiring a complex setup. Both Compellent and Xiotech offer monitoring and support services similar to those the tier-one storage vendors provide to large enterprises, allowing customers to respond proactively to projected failures.

[ See also: Fast guide to fancy SAN management ]

Great strides have also been made in ease of setup and administration. For instance, configuring a partition on the Compellent system to be remotely replicated on a second system hundreds of miles away was literally a two-minute job.

The three systems range in price (as tested) from $21,195 to $76,813, but with the price as configured it is difficult to make an apples-to-apples comparison. Capacity is not merely a matter of number of drives times drive capacity -- all of these systems support multiple tiers of storage, using 15K, 10K and 7.2K FC drives as well as the enormously less expensive and higher capacity (though slower and less reliable) SATA drives. Xiotech even offers an SSD (solid state disk) option that offers an extreme performance gain at a much higher cost per gigabyte -- a 6GB solid state module that fits into the same drive bays as the other disks.

System performance will greatly depend on a number of factors, including the types of drives installed, interface speeds, servers connected (operating system, drivers, HBAs installed, software in use), RAID levels of the partitions in use, number of drives in the partition, and the name of the administrator’s favorite cartoon character. Although the Xiotech system offers the ultimate in performance with SSD drives, the fact that a 6GB SSD drive is more expensive than a 750GB SATA drive will limit SSD use to the most performance-critical applications, such as database indices. Due to the varying numbers and types of drives, I did not attempt to measure performance across the systems, but instead focused on testing the features to ensure they performed as expected.

Compellent Storage Center

The Storage Center I received from Compellent came in two pieces: a Storage Center appliance and one 16-drive enclosure, which was equipped with eight 300GB 10K drives and eight 500GB 7.2K drives. The Storage Center can be used as a single controller for multiple enclosures, or dual controllers can be used for redundancy. Each enclosure supports three different classes of FC drives -- 15K, 10K, and 7.2K -- as well as SATA drives. The system as shipped came with 6.4TB of raw capacity, more than the others, and not at the highest price.