Release 10.1A: OpenEdge Getting Started:
Database Essentials

> ## Comparing expensive and inexpensive disks

> When you buy a disk, you are really buying two things: storage capacity and throughput capacity. For example, if you want to buy 72 gigabytes (GB) of capacity, you can purchase a single 72GB unit or four 18GB units. The storage capacities of these disks are exactly the same, but the four-drive configuration has potentially four times greater throughput capacity. Each drive is capable of doing approximately 100 input/output (I/O) operations per second regardless of its size. Therefore the four-drive system has the potential to perform 400 I/O operations per second.

> It is generally less expensive to purchase fewer larger disks to get to your desired capacity for a number of reasons. First, the 72GB drive is only marginally more expensive than a single 18GB drive, so buying four 18GB drives to obtain the same capacity as a 72GB drive will substantially increase your cost. Second, you must have the rack space to hold these drives; more rack space can lead to additional cost. Third, you might need more controllers to efficiently run the additional disks, also adding to the cost.

> However, if performance is important, you should have a greater number of physical disk drives to give you the greatest throughput potential. The additional cost of the multi-disk solution is offset by increases in performance (user efficiency, programmer time, customer loyalty, and so on) over time. If you are only using the database as archival storage and you do not care about the performance of the database, fewer large disks are recommended to decrease cost. This approach allows you to store the greatest amount of data on the fewest number of disks.

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