iSCSI accounts for only two percent of the SAN market, but its low cost and ease of use are positioning it for growth.
Network Computing examined four iSCSI modular SANs; its Editor's Choice ran circles around the competition.
We tested four dedicated iSCSI SANs in our Green Bay, Wis., Real-World Labs®: EMC's Clariion CX300i, EqualLogic's PS200E, LeftHand Networks' LeftHand SAN with Network Storage Module (NSM) 150 and MPC Computers' DataFrame 420. We also sent invitations to Aberdeen, which declined because its product is still in development, and Raid, which turned us down because of prior commitments. Relatively few vendors have committed to building dedicated iSCSI SANs. Instead, many are easing their way into this market by adding support for virtual, block-level iSCSI volumes to their NAS (network-attached storage) products. Although these solutions offer a level of convenience for environments that require a mix of file- and block-level storage (see "IP Storage Devices"), we chose to maintain our focus on SAN-specific products dedicated to providing block-level storage.
Three of those products--the EqualLogic, LeftHand Networks and MPC--are independent SAN modules that can be virtualized into a dynamically scalable storage environment and targeted in the sub-100-TB range. This building-block premise takes advantage of the power of multiple storage controllers and linear bandwidth increases through the clustering of multiple modules and their active Gigabit Ethernet ports.
The EMC, by contrast, uses the conventional SAN model: A centralized storage controller manages multiple dependent disk arrays. Although this architecture reduces the cost of additional disk arrays, the CX300i supports a maximum of 60 drives and tops out at 19.2 TB. Additional drive cabinets are linked with dual FC loops, but because the number of available Gigabit Ethernet ports stays the same even when you add drive enclosures, beware of the potential for bandwidth bottlenecking as the system hits its maximum capacity.
All four systems have features we consider basic to an iSCSI SAN environment: dynamic volume expansion, provisions for snapshots and replication, support for CHAP (Challenge Handshake Authentication Protocol), iSNS (Internet Storage Name Service) discovery and LUN (logical unit number) masking. In all cases, additional disk arrays can be added to the storage pool, managed from a centralized console and assigned without the interruption of production, though array performance will be reduced during reallocation. Every SAN we tested came fully loaded with drives in every slot, though each one lets you minimally configure it with three to five initial drives while offering a range of drive-size options for future growth. For more information, see our features chart.
In our real-world performance tests, the EqualLogic dominated the competition, with MPC and LeftHand Networks following at a distant second and third. For reasons EMC and Network Computing couldn't resolve at deadline, the CX300i had severe problems with Iometer read tests larger than 64 KB and produced questionable results from the matching write tests, even though smaller transfers worked as expected. Because all the other systems performed these tests under identical conditions and with repeatable results, we had no choice but to give EMC a low score in performance.
We compared the features, performance, management, scalability and price (both list and cost per terabyte) of all four systems. It was a relatively easy call to present our Editor's Choice award to EqualLogic. The PS200E Storage Array has noteworthy ease of use, and its performance ran circles around the rest. LeftHand Networks' NSM and MPC's DataFrame share common software, but the DataFrame has the lowest cost per terabyte, while LeftHand's product offers growth through smaller modules. EMC's Clariion has the widest matrix of configuration options and would be a great fit for environments with an installed base of EMC gear, but it tops the list in price as it unexplainably bottomed out in performance.
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