Hard drives can slow down when frightened! Engineers shout at the server, and HDD read/write speeds drop sharply as a result.

In 2008, an engineer shouted at a server rack, causing a sudden spike in hard drive latency. This video has recently gone viral again, revealing a physical law in Silicon Valley that has never truly been solved.

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• What happened during the shout in 2008
• How sound waves cause the read/write head to "get lost"
• 17 years later: The unfinished challenge between AI data centers and physical laws

Yelling into a row of server racks, with monitoring curves on the screen suddenly surging upward at the same second? According to an archaeological report by HKEPC today, a real data center experiment video from December 2008, titled "Shouting in the Datacenter," has recently been circulating again on social media, with over 5.3 million views.

The main subject of the video is Brendan Gregg, who was working at Sun Microsystems at the time and is now an engineer at OpenAI. The video was uploaded by his colleague Bryan Cantrill; Gregg himself admitted in an interview that he had almost forgotten about it, and it was only the video's resurgence that reminded him. This less-than-two-minute clip has become a mythic teaching material in the hardware engineering community.

What happened during the shout in 2008

The experiment took place in a JBOD (simply "a bunch of hard drives directly connected together") rack.

In the video, Gregg approaches the rack and shouts loudly at the densely packed mechanical hard drives (HDDs). Simultaneously, an analysis tool developed by the Sun Microsystems Fishworks team monitors in real-time the internal latency of each hard drive (simply put, the waiting time from receiving a command to actually starting to read/write data).

The result is very clear: when Gregg shouts, the latency numbers of the affected HDDs immediately spike, causing read/write speeds to plummet; when he stops, the curves gradually return to normal. The monitoring screen precisely indicates which drives are affected and to what extent.

How sound waves cause the read/write head to "get lost"

Why does this happen? The inside of an HDD is a micro world so precise it’s almost unbelievable: disks made of aluminum, copper, or ceramic spin at thousands of revolutions per minute, with read/write heads floating just a few nanometers above the disk surface to move and position. The entire system’s fault tolerance, measured on a human scale, is nearly zero.

When a person loudly shouts near the rack, sound waves propagate through the air to the HDD casing, then transfer through the casing structure into the interior, causing tiny relative displacements between the disk and the head. The read/write head must precisely align with the data tracks on the disk; any unexpected micro-shift triggers a re-positioning process, increasing latency and decreasing throughput.

While enterprise-grade HDDs are equipped with shock resistance designs and can withstand some background noise (air conditioning, fans), sudden high-intensity sound pressure can still breach protective thresholds. This is not a design flaw but a structural limitation of mechanical spinning disks in the face of physical laws: disks fear vibrations, and sound is vibration.

Another more widely known and even more absurd case caused this phenomenon to be officially recorded as a security vulnerability. In 1989, Janet Jackson released the single "Rhythm Nation," which, according to a Microsoft engineer, had a natural resonance frequency that coincidentally matched the mechanical resonance frequency of mainstream 5400 RPM laptop HDDs at the time.

Playing this song near some laptops could directly cause the hard drives to crash. Not only on the same computer, but even on nearby laptops. This case was eventually officially recorded as a security vulnerability CVE-2022-38392, making it a rare example in the history of hardware and software security where a popular song was the cause of a vulnerability.

17 years later: The unfinished challenge between AI data centers and physical laws

Currently, the AI wave is accelerating data center expansion at an unprecedented pace, with increasing demands for computational density, storage density, and stability.

SSD (solid-state drives with no moving parts, storing data in flash memory) have greatly penetrated both modern data centers and consumer markets, with transfer speeds orders of magnitude faster than mechanical HDDs, and almost immune to sound waves, vibrations, and physical shocks: no disks, no heads, and thus no risk of the head "getting lost."

However, due to cost and capacity advantages, mechanical HDDs are still widely deployed in cold storage scenarios. The raw data sets required for AI training often reach tens or hundreds of terabytes, with a significant proportion still stored on disk arrays. This means that "sound waves causing HDD slowdown" is not just a historical curiosity but a potential risk in current infrastructure.

This 17-year-old video has recently gone viral again, perhaps because of this reason: even in the most modern data centers, operations still run under the influence of physical laws that can be disturbed by a shout.