John Henry offers greater flexibility and higher performance than most custom solutions built at a cost of many programmer-months or years. Cost advantages John Henry is optimized for inexpensive PC hardware running Windows NT or Windows 2000. Performance John Henry is optimized to process an entire data set, rather than transactions or queries. As a result, it is often hundreds of times faster than transaction-oriented databases, even those running on expensive hardware. But the real key to John Henry's superior performance is sequential disk access .
Sequential access means that records are read in the order in which they are stored on disk.
Sequential access is fast because each successive record is read from the next position on the disk, which allows data to be read in large blocks. Random access, by contrast, reads each record from a location that is appropriate for the software, but which does not bear any relation to the physical storage on disk. Random access is slow because the disk head must move to access each record. All operate on entire tables. Thus, no matter how you connect the tools together, you cannot create a low-performance data processing engine.