What does this icon mean?

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(a) The disk 500GB is nearly full.

(b) The disk 500GB is about to fail.

(c) The disk 500GB is running at turbo speed.

When I polled a group of people on Twitter, the correct answer (c) was chosen by about a third of people. Most people picked (b): “It looks like it’s about to blow, Captain!”

The icon appears when you install Western Digital’s drivers. It’s meant to show that the disk is in turbo (high speed) mode. But there’s something not right about that needle pointing to the red zoneā€¦