Cylinder – Combination of the Same Tracks on Different Discs [MiniTool Wiki]
Cylinder refers to the combination of the same tracks on different discs. The number of turns of concentric circles ( track ) on disc is the number of cylinder. These tracks have a same magnetic filed rotating direction. If there is a dead pixel on one track, the track will be abandoned, because this track can't constitute a path. This is just like the situation where a piece of wire is broken down in series circuit.