Chapter 8: Disk Optimization: Optimum or Not?

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Some vendors tout a feature that is said to go beyond defragmentation. Known as disk optimization or file optimization, it is said to reduce the time it takes to recover data from disks as well as the time it takes to defragment. Disk optimization involves the intelligent placement of files on a disk in order to minimize head movement and process read/writes faster. It is an intriguing theory that software developers have flirted with for over a decade — improving performance by strategically positioning files. But, how effective is it in the real world? For the average consumer on a low-end PC, optimization appears to produce some benefit. Where it may fall short, however, is in the enterprise. The simpler the disk I/O model, the greater the potential for achieving some type of improvement in performance from optimization. With regard to RAID and enterprise environments, however, disk optimization begins to look a little shaky. According to some experts, optimization may sometimes reduce performance in the enterprise due to the resources used to optimize a disk as well as the complexity of modern disk architectures.

Hard Drives Are Slow

The relatively slow pace of disk rotation represents a serious performance bottleneck in modern systems. Just compare disk velocity to the rest of the key hardware components:

  • CPU: Even low-end central processing units (CPUs) now surpass the billion operations per second mark. At the high end, they exceed 2 billion operations per second.

  • Memory: Memory (or RAM) is calculated in millions of operations per second. Although it compares poorly with CPU velocity, the speed is already more than sufficient to serve up good-quality streaming audio and video over the Internet.

  • Hard Disk: With good disks peaking at about 10,000 rpm, disk access is pinned at around 200 operations per second (five milliseconds per seek).

Thus, the CPU in a $500 computer operates almost one million times faster than the best hard disks on the market. It is no wonder, then, that anything that comes along claiming to improve disk performance is greeted with enthusiasm in the IT community.

Unfortunately, the liabilities of slow hard drives have much deeper ramifications due to fragmentation. Most operating systems are subject to severe fragmentation after several months of activity. It is quite common to find files that are in hundreds or even thousands of pieces. If a file is split into 200 pieces, for example, it takes one second to access a unit of information rather than five milliseconds. So, as the CPU roars on in the gigahertz range, fragmentation reduces the disk speed to a relative snail's pace.

The most time-honored solution to this performance hit is defragmentation, which consolidates file fragments into contiguous blocks, thus cutting down read/write times. Modern networkable defragmenters are able to produce gains on sluggish servers and workstations that are comparable to major hardware upgrades.



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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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