Disk-based VLBI recording

Ever since the first VLBI experiments in 1967, magnetic tape has been the mainstay medium for recording VLBI data. However, in late 2000 it became evident that the price of computer disks was dropping far faster than that of computer magnetic tape, and would likely drop below the price of tape within a few years. Additionally, disks have the advantages of relatively high data-rates, random access and easy availability. Used in disk arrays, data rates of 1 Gbps are readily achieved. These realizations have led to the development of several disk-based systems for VLBI data, including the Mark 5 system in the U.S., the K5 system in Japan and the PC-EVN system in Europe. We will examine the current state of disk-based VLBI systems, their expected future, and their close relationship to the developing technique of e-VLBI.