Bryan Cantrill
4 HN recommenders · recommended in 18 months, 2011–2026
2:00 · 5.7M views · Dec 31, 2008
A two-minute 2008 clip from Sun's Fishworks team in which Brendan Gregg uses DTrace to show disk latency spiking while he shouts at a rack of drives. Bryan Cantrill narrates the demonstration.
It is the go-to viral demo whenever HN discusses vibration, acoustic attacks, or sound affecting hard drives.
20 comments from Hacker News
I had the "vibration" problem a few times in me IT career, train, construction work and once elevators. It is the kind of issue that are really hard to diagnose the first time but after the first time it's part of the standard "diagnose suite". I love to show this video about the effect of noise on HDD (be sure to put the volume down) this video
The paper links to this entertaining YouTube video from 2009, in which someone demonstrates the effect by literally shouting at a rack of servers: this video (EDIT: replaced the link I found via YouTube's search with the original, thanks robotmlg!)
One of the little gems I found while I was putting together the video for this post was "Shouting in the datacenter", an older clip (from the pre-HD era) demonstrating the consequence of doing exactly what the title says: this video Warning: loud!
Also interesting: a Sun engineer uses dtrace to show HDD latency spiking after he yells at his disks this video
+1, in general. To adda bit of content: 1) Power Hungry, the total power envelope of a rack position is the limiting issue. You can fit 16-20 disks per RU no problem. The constraint on total density is your 5kVa or 10kVa power budget. Watts matter. 3) sensitive to vibration, be very very quiet this video 4) Density, actually 4TB is hitting the sweet spot for $ per byte last time I looked. If you need absolute density look for 5 & 6TB Real Soon Now. If you can tolerate some loss variable density disks around 5TB look quite a bit more cost effective. 5) Read ahead, you only need to read ahead by a couple of chunks. For video ball park it at 2MB. You don't really need lots of RAM, think 32-64GB per chassis. Additionally each 8GB dimm costs about the same power as a disk. By going with 32GB instead of 64 I can fit another 2-3 disks in the power budget per chassis.