[pjdesno]

I love the visuals, and if it's ok with you will probably link them to my class material on block devices in a week or so.

One small nit: > A typical random read can be performed in 1-3 milliseconds.

Um, no. A 7200 RPM platter completes a rotation in 8.33 milliseconds, so rotational delay for a random read is uniformly distributed between 0 and 8.33ms, i.e. mean 4.16ms.

>a single disk will often have well over 100,000 tracks

By my calculations a Seagate IronWolf 18TB has about 615K tracks per surface given that it has 9 platters and 18 surfaces, and an outer diameter read speed of about 260MB/s. (or 557K tracks/inch given typical inner and outer track diameters)

For more than you ever wanted to know about hard drive performance and the mechanical/geometrical considerations that go into it, see https://www.msstconference.org/MSST-history/2024/Papers/msst...

[bddicken]

Whoah, thanks for sharing the paper.

[pjdesno]

I reviewed it three times for different conferences :-)

I’m still annoyed they didn’t include the drain time equation I used for calculating track width, which falls out of one of their equations.

Oh, and I’m very glad you showed differing track sizes across the platter. (BTW, did you know track sizes differ between platters? Google “disks are like snowflakes”)