What if a holographic storage drive were invented? Suppose that a holographic dr

Question

What if a holographic storage drive were invented? Suppose that a holographic drive costs $10,000 and has an average access time of 40 milliseconds. Suppose that it uses a $100 cartridge the size of a CD. This cartridge holds 40,000 images, and each image is a square black-and-white picture with resolution 60006000 pixels (each pixel stores 1 bit). Suppose that the drive can read or write 1 picture in 1 millisecond. Discuss the following questions.

a. What would be some good uses for this device?

b. How would this device affect the I/O performance of a computing system?

c. Which other kinds of storage devices, if any, would become obsolete as a result of this device being invented?

Explanation / Answer

a. This device holds about 4.5 MB per image, the streaming transfer rate is about 4.5 GB/s, and the total capacity per cartridge is about 180 GB. Using the techniques of question 14.7, the transfer size needed for 25% utilization is 60 MB. A drive with a single cartridge has a cost per gigabyte of about $56. By comparison with magnetic hard disk, the streaming transfer rate is nearly 1000 times higher, the cost is about the same, but the practical transfer size is very large. So this technology will not replace magnetic disks, but could work well as the tertiary-storage component of a hierarchical storage system. It would also be suitable for high-speed data storage, such as for satellite telemetry data. The cost of storage for a cartridge

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