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Unformatted text preview: esting facts about the IBM disk. First, more tracks are packed into the outer zones (which have a larger circumference) than the inner zones. Second, each zone has more sectors than logical blocks (check this yourself). The unused sectors form a pool of spare cylinders. If the recording material on a sector goes bad, the disk controller will automatically and transparently remap the logical blocks on that cylinder to an available spare. So we see that the notion of a logical block not only provides a simpler interface to the operating system, it also provides a level of indirection that enables the disk to be more robust. This general idea of indirection is very powerful, as we will see when we study virtual memory in Chapter 10. End Aside. 6.1.3 Storage Technology Trends
There are several important concepts to take away from our discussion of storage technologies. ¯ ¯ Different storage technologies have different price and performance tradeoffs. SRAM is somewhat faster than DRAM, and DRAM is much faster than dis...
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