A home-built virtual RAID with ATA over Ethernet

Failure of Target or Initiator

If one target fails, this is basically nothing more than the failure of a hard disk in a normal RAID array. You only need to replace the defective unit with a fully functional one, and you can replace a physical hard disk with a raw image on a different machine, for example.

The new disk just needs to be the same size as the original; you can then share it via vblade-persist. For example, if you want to remove the failed device connected to e2.1, you would simply issue the following command;

mdadm /dev/md0 --remove /dev/etherd/e2.1

then add the new device (e4.1 in this example) to the RAID array:

mdadm /dev/md0 --add /dev/etherd/e4.1

In the background, the software will now start the rebuild process, which may take several hours to complete depending on the size of the system.

However, if an initiator fails, the array simply can be rebuilt on a new system. In this case, you can restore the previously saved configuration or run mdadm directly:

mdadm --assemble /dev/md0 /dev/etherd/e1.1 /dev/etherd/e2.1 /dev/etherd/e3.1

In this case, the command restores the RAID on another system.

Conclusions

ATA over Ethernet is a promising protocol that greatly simplifies many tasks. Used correctly, AoE facilitates the work of administrators and forensic experts; in many cases, you can even virtualize RAID structures.

The Author

Dennis Schreiber is a computer forensics scientist with the financial authorities in the German state of Thuringia. When he's not hanging out with family and friends, he experiments with Linux and computer forensics or takes his bike for a spin.

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