What is ATA over Ethernet?

Kurt Inman

Advanced Technology Attachment (ATA) Over Ethernet is a protocol for communicating with storage devices over a local area network (LAN). Also known by the acronym AoE, ATA Over Ethernet is a low-level network protocol. It does not require the additional overhead of Transmission Control Protocol (TCP) or Internet Protocol (IP). It is often used by embedded systems to access Serial ATA (SATA) disk drives and other storage devices. It can also be used as the basis for a Storage Area Network (SAN) made from common, low-cost components.

An Ethernet cable.
An Ethernet cable.

The ATA Over Ethernet protocol simply encapsulates ATA commands and responses used by SATA and Parallel ATA storage devices. This allows streamlined commands to travel over an Ethernet LAN instead of a standard storage device cable. A computer with an AoE driver loaded can access an ATA device on the LAN as if it was connected to the local system bus. Lack of a higher-level protocol prevents the AoE packets from traveling across the Internet or even beyond a local network switch.

Ethernet cables plugged into an Internet switch.
Ethernet cables plugged into an Internet switch.

AoE does not include specific encryption, password or security features. The local area limitation of ATA Over Ethernet does prevent distant hackers from accessing the storage data, however. The file system or the storage device itself may also include access lists and other security measures. If more advanced security or file sharing across a broader network is needed, Internet Small Computer System Interface (iSCSI) may be a better solution.

ATA Over Ethernet is relatively easy to implement and introduces very little overhead to the transfer of storage data. It is supported by many operating systems either natively or with third-party software. Linux® and UNIX® variants often support AoE, as does Microsoft Windows®. Some companies make SAN appliances that communicate via the AoE protocol, including Network Attached Storage (NAS) units.

When multiple systems share a storage device networked with ATA Over Ethernet, they must coordinate simultaneous access to individual files. This can be done without an extra file system or server by using a cluster file system such as Global File System (GFS) on the storage device itself. On a simpler level, the AoE protocol includes a locking mechanism to indicate when the target storage device is in use by another host.

Backup storage is a good application for ATA Over Ethernet. The protocol provides an easy means to use inexpensive hard drives to back up a system or a whole network. Using AoE the storage devices can be local or even somewhat remove, depending on the length of the network connection.

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