d disks (the Samsung V5400 for example and the 3-GB SGH-i300 launched in the UK) and Toshiba brought forward the availability of a 4-GB 0.85-inch hard disk but in practice over the past six years solid-state memory has eclipsed all other options for mobile applications. A hard drive remains the most economic and space effective way to put a terabyte of storage on your desk top but is not optimum in a mobile product form factor. 9.4.1 DV Tape versus DVD versus Hard-Disk Cost and Performance Comparisons Tapes may well continue to disappear from the market but they still offer good value for money. A mini DV tape costing 4 dollars implies a storage cost of less than 0.04 of a cent per megabyte but the memory medium cannot be used for random access applications. Making Telecoms Work An optical disk could potentially offer similar cost/performance ratios with the added benefit of sequential storage and random access capability. A 4-GB microdrive can provide sequential storage and fast random access (15 milliseconds rather than the 75 milliseconds of a DVD) but presently costs about 10 cents per megabyte and as we have stated is nonoptimum when used in portable products. 9.4.2 Hard-Disk Shock Protection and Memory Backup A number of manufacturers (Toshiba for example) have MEMS-based accelerometers built in to hard-disk drives to detect when a product is being dropped. The head can then be kept clear of the disk to prevent damage. Analogue Devices (low-g iMEMS) and Microelectronics have digital accelerometers targeted at hard-disk protection. This is standard now in most lap tops though if you have dropped a lap top your problems may be more fundamental than just a damaged memory. Also, lap tops increasingly are going to solid-state memory linked to cloud connectivity, what used to be called the thin client model. 9.5 Solid-State Storage This thin client model has mixed implications for the solid-state memory market. On the one hand, there is an increasing need for short-term storage but thin clients linked to cloud co