Server Issues

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Using optimization on enterprise servers has been likened by some to playing craps at Las Vegas — sometimes you win, more often you lose. In all probability, optimization is as likely to worsen system performance as to improve it. One reason optimization tends to fail to enhance server disk performance is its reliance on specific user access patterns. As soon as you add several users into the mix, patterns tend to become cloudy. Add thousands of users accessing dozens of programs, and the concept no longer sounds so impressive.

As noted earlier, the simpler the disk pattern, the better the chance that optimization may make a small difference, but, as progressive complexity enters in, it may actually become a performance liability. This becomes apparent when one looks at how optimization applies in a network run by a busy server. Instead of one user opening one document, the network has hundreds of users. Scores of applications are running simultaneously, and thousands of files are being accessed at any given time. In this random mode of operation, where does a disk optimization program place files, and will that placement have any impact on head movement? NSTL makes the point that even infrequently used files may be accessed enough that the effect on performance of strategic placement (optimization) is essentially immeasurable. Take databases, for example. Most people access a few specific entries, and it is rare that the entire database is accessed or updated in one unit of time; therefore, as databases are normally organized as one huge file, they contain both high- and low-frequency access information. So, where does the optimizer put them? Placed at the front of the disk, they take up a lot of space and could potentially slow I/O by pushing other frequently accessed files closer to the center of the disk. When positioned at the end of the disk, however, users could face delays in waiting for information that is called up constantly. Thus, most databases represent a lose-lose proposition for optimization programs.



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Server Disk Management in a Windows Enviornment
Server Disk Management in a Windows Enviornment
ISBN: N/A
EAN: N/A
Year: 2003
Pages: 197

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