2005/05/29 AoE (ATA over Ethernet) distributed storage

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© May 2005 Tony Lawrence

The idea here is that for local network storage where you and the storage are connected to the same switch, you don't really need the overhead of tcp/ip. Packets don't get lost traveling through a switch, they don't get reordered, so why have all that overhead? AoE is a protocol designed to provide the minimum overhead necessary for you to have (for example) /dev/etherd/e0.0 as a block device that refers to storage out on the lan, but that you would treat no differently than you would /dev/hda. It's a great idea, and the driver that accomplishes this magic is in the 2.6 kernel.

Of course that's only half the story. There has to be something at the other end of the network that talks back over the same protocol, and that is NOT in the kernel. There is a "vblade" project that can provide that functionality, and a line of commercial hardware products also (http://www.coraid.com Coraid - link dead).

The June issue of Linux Journal has an article about ATA Over Ethernet: Putting Hard Drives on the LAN . This article is written by a Coraid employee, so it isn't entirely unbiased. There was a long thread at http://lists.ssc.com/ but that site is gone now. Note that the "vblade" project referred to above is authored by the same Coraid employee who wrote the article, but he is quite direct in pointing out that "The AoE network protocol is open---anyone can implement it".

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