AoE (ATA over Ethernet) Technology

AoE Protocol

• Coraid EtherDrive products use the AoE protocol to connect disks to servers using Ethernet.
• ATA-over-Ethernet (AoE) is a thin protocol layer directly on top of Ethernet.
• ATA disk commands (ie. read disk sector x, write disk sector y) are put directly into standard Ethernet frames using the AoE protocol. AoE is a block storage protocol.
• AoE is a non-routed protocol, therefore does not require IP or TCP protocol layers. This eliminates unnecessary processing and makes network connection to disks simple.

AoE Driver

• An AoE protocol driver in the host operating system provides the initiator function for the host to access storage connected to an Ethernet port.
• The AoE driver bridges the operating systems block device driver interface to the hosts Ethernet driver. This allows the host to use a standard Ethernet NIC
• AoE target devices (ie. EtherDrive disk storage appliances) connect via standard Ethernet.
• AoE can work with any OS. An AoE driver is inside the main Linux kernel. Drivers are available for Linux, FreeBSD, Solaris and Windows.
• AoE target devices are just like local disks. They can be used like a normal hard disk drive, but since they are network connected, the disk can be shared with any network connected host.
• AoE target devices can be partitioned like a normal disk, and supports any filesystem like a normal disk.

AoE is Block Storage

• As with any block storage device, the host operating system can also create RAID sets from AoE devices.
• The AoE block devices can be managed with storage virtualization tools like logical volume managers and other volume management tools.
• AoE devices naturally work with disk-to-disk backup software and virtual tape library software systems designed to work with hard disk drives.
• AoE devices work with any filesystem or as directly accessed disks as is required by database applications.

Shared Storage

• A single AoE device can be partitioned.
• Each partition can be accessed by a separate server or application.
• Each partition can have its own unique filesystem (ie. EXT3, JFS, XFS, Reiser, etc.).

Cluster Shared Storage

• A single AoE device can be shared if a cluster filesystem is used (ie. GFS, Lustre, etc.).
• The AoE protocol can be used for unrestricted access to the disk volume or can be used to apply access rules.
• Using port based VLAN access zoning can be established.
• Coraid's SATA+RAID EtherDrive storage appliances (SR1520 and SR420) also support optional MAC address filtering to restrict server access for each logical AoE device.
• Coraid's AoE storage devices support a "configuration string" which is written to the storage device. Once enabled, the config string can be used to restrict disk access to only hosts that use the config string in their AoE storage requests.