Latency impact of sonic waves directed to hard disk casings
When you really thing about harddisks, you could get the feeling, that this subsystem is a really delicate one. You read data from disk spinning at up to 15.000 rpm, trying to catch tracks as narrow as 50 nm, and you don´t read the data from the hard disk, you read a waveform and compute the most probable data pattern out of it. All together it´s a little bit of an suffciently advanced technology indistinguishable from magic.But at the end the system “harddisk” is really susceptible for perturbations from outside. Brendan Gregg was able to measure the latency impact of sonic waves hitting the casing of hard disks - with a low-tech approach as he wrote in Unusual disk latency.
I don´t want to know how he found out about this effect … perhaps a debugging session or a harddisk falling on his feet. Nevertheless it´s an impressive usecase for the Analytics feature of our new 7000 series storage. Try to find such effects with the tools from our beloved competitors. Their products are susceptible for “Brendans war scream” as well (as they use hard disks, too) … but you can´t measure it.