sentences:  The usable capacity of a RAID 01 array is the same as in a RAID 1 array made of the same drives, in which one half of the drives is used to mirror the other half.formula_1, where formula_2 is the total number of drives and formula_3 is the capacity of the smallest drive in the array.At least four disks are required in a standard RAID 01 configuration, but larger arrays are also used.