The letter is the arrangement of the copies:
 n - near copies: Multiple copies of one data block are at similar
     offsets in different devices.
 f - far copies: Multiple copies have very different offsets
 o - offset copies: Rather than the chunks being duplicated within a
     stripe, whole stripes are duplicated but are rotated by one
     device so duplicate blocks are on different devices.
Asekkil d asemyizwer n wanɣalen:
 n - anɣalen i iqerben: Aṭas n wanɣalen n yiwen yiḥder n yisefka ad ilin
     kifkif n tiggiyin deg yibenkan yemgaraden different devices.
 f - anɣalen i imbaɛaden: Aṭas n wanɣalen ɣur-sen aṭas n tiggiyin yemgaraden
 o - anɣalen n tiggit: Ideg tiḥedrin ad ttuselgent deg
     tesfift, tiḥedrin tummidin ttuselgent maca ttwazzint s yiwen
     yibenk akken iḥedran yettuselgen ad ilin ɣef yibenkan yemgaraden.