Alternative SANs

Despite economic uncertainty, we still think this was a good year for storage.

New technologies such as iSCSI and Serial ATA moved from the drafting board to the market and promise further interesting developments. Increased competition among FC (Fibre Channel) gear vendors has resulted in more affordable solutions and better manageability. Moreover, the future promises a combined FC and iSCSI network that will make networked storage even more pervasive and flexible to meet business requirements.

However, at least one company is not fostering this idyllic iSCSI-FC relationship. We are referring to Boulder, Colo.-based LeftHand Networks Inc. and its NUS (network unified storage architecture), which promises an Ethernet-based SAN without committing to either FC or iSCSI protocols.

How does it do that? The main building block of a NUS is the NSM (Network Storage Module), a 1U box that hosts up to 480GB of ATA storage, plus processors and a Linux-derived OS capable of conversing with similar units to provide seamless virtualization, replication, and fail-over.

To make it all happen, put together as many NSMs as needed to build a SAN with adequate capacity, then install a tiny piece of software, AEBS (Advanced Ethernet Block Storage), on your servers. AEBS, as the name implies, provides block-based access to NSM storage.

For NUS management, LeftHand developed management software (another acronym, SCC, for Storage Control Console) that will typically reside on administrators’ PCs. From the Java-based SCC console, you can allocate volumes across multiple NSMs for better performance, set thresholds to avoid running out of space, and reserve spare NSMs in case of hardware failures.

We found LeftHand’s approach to striping and replication especially interesting. You can set up volumes that stripe across multiple NSMs, and also define replicas for improved resilience and performance. The additional twist is that each data snippet is automatically striped and replicated according to centralized rules, ensuring that a failing NSM will not compromise data integrity because at least one copy of the volume’s data is replicated on other NSMs.

Also, given enough storage space, you can set up as many volume snapshots as needed; LeftHand’s software prescribes no hard limits. Being that the NUS is IP-based, it’s easy to set up a multisite configuration that extends the same data integrity logic to NSMs at remote locations.

Factor in that a NUS automatically switches to a spare NSM module if one fails and that a nearly instant extension of the storage pool can be achieved by adding other NSM modules, and you essentially have a SAN that promises to rival FC and iSCSI alternatives in cost and flexibility.

Mario Apicella is a senior analyst at the InfoWorld Test Center. Scott Tyler Shafer is an InfoWorld reporter. Contact them at