I want a little device, a System on Chip perhaps, that has SATA on one end and a CAT-5 jack on the other. Add storage to your network by... adding storage TO your network. All you would need is some distributed filesystem to spread the love over all your directly attached network devices.
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Barring that, devices exist that have an eSATA port and an RJ45 port. Pricey, but existent.