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Coraid and ATA-Over-Ethernet Technology

The Key Technology Enabler for Coraid’s Resilient Scalable Architecture

Data server admins are always on the lookout for changes in the industry that will help do their job better, keep their data safer, and speed up file access. The old standbys in recent years have been iSCSI and Fibre Channel. These high-speed technologies have been good matches for storage applications like database use and management where use can be intense. They can, however, be quite costly to keep up and running properly and they require a lot of care and maintenance. A new alternative to iSCSI and Fibre Channel is ATA-Over-Ethernet (AoE).

This open-source connectionless storage networking protocol was originally developed in 2003 by California company, Coraid. It connects servers and storage in a less complex fashion than iSCSI and Fibre Channel. The AoE Layer 2 design works to find the most efficient way to transmit raw disk I/O commands over raw Ethernet. The more connects that are added, the more bandwidth that is made available, the more resilient the pathways. It is important to note that AoE is not iSCSI. The only commonality between AoE and iSCSI is that they both use Ethernet for transport. iSCSI uses TCP/IP at Layer 4 and AoE Layer 2.

Like Fibre Channel, iSCSI is a connection-based topology, which requires sequenced serial delivery of the data packets of the network. No matter how many iSCSI ports you have on your servers and storage, only one can be used at a time to transmit data due to the connection requirement. Other ports can be used in "round robin" to increase throughput.

When transmitting data in an AoE network, jumbo frames should be enabled as it allows each 8K block to occupy a single Ethernet frame for maximum transfer speed. AoE uses all available ports automatically and does not require sessions or sequence numbers. Frames can arrive out of order without an issue.

There have been questions from the admin community as to how secure AoE is as compared to other protocols. Some worry that is isn't as secure as iSCSI since there is no authentication. This, however, is not the case. As AoE is not accessible via a router and must physically connect to the local Ethernet switch, thus greatly reducing the possibility of unauthorized access. You are simply not able to route the packets so people outside don't see your data.

Generally speaking, an AoE setup is two to four times more efficient than iSCSI. And as mentioned previously, it is important to remember that AoE is not simply a variation on the theme of iSCSI. It is its own separate transfer protocol.

So what does this all mean when it comes to day-to-day data management?

It means AoE is a valid alternative to iSCSI and Fibre Channel. With fewer protocol layers, AoE is fast and easy to implement. It provides scalability along with performance.

More Stories By Sara Williams

Sara Williams is a consultant at Coraid. Coraid is a leading provider of network storage solutions. Coraid delivers scale-out performance, Ethernet simplicity, and an elastic storage architecture to handle massive data growth. Designed from the ground up for virtualization and cloud architectures, Coraid's platform has been deployed by more than 1,700 customers worldwide.