[smachiz]

It's a bit funny, but it's really a question of distance more than medium.

For in-rack, DAC/Twinax is just copper and good for 400G, and cheaper than separate optics and fiber.

[sillystuff]

And, DAC has lower latency and uses less power than 10GBASE-T even at the lower 10Gb speed (e.g., due to latency you don't want storage over 10GBASE-T). And, DACs contain fewer parts that can fail than optical transceivers (esp. short passive DAC cables) so more reliable (as long as not physically manipulated) than fiber + optical transceivers.

DAC cables are a bit harder to route than fiber though.

[sillystuff]

That should read:

And, DAC has lower latency and uses less power than 10GBASE-T (e.g., even at the lower 10Gb speed due to latency you don't want storage over 10GBASE-T).

(Not that anyone is still reading this old article or would likely care if they were)