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Review: iSCSI Modular SANs

iSCSI Modular SAN Performance

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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.

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