6.3.8 Linearly and Helically Scanned Tapes Data tapes may be written or read with a fixed head, generally described as linear, or with a rotating or helical head. Linear tapes typically follow a serpentine track layout, and it has been argued that this shuttling can lead to wear or a so-called shoe-shine effect. In practice, modern tapes are designed to last for large numbers of passes, however, it is still prudent to access frequently used content from hard disc. Tapes, which experience chemical decomposition from hydrolysis and other causes, will usually run better over fixed guides and components in the tape path at speeds of around1-2 m/s or greater, which are typical of fixed- head or linear formats. Rotary-head or helical formats typically have higher tape-head speeds which create a greater air-bearing effect between the tape surface and the read-write heads, but the linear tape speed over the fixed guides and heads is much slower, so this is where fouling often occurs.