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NTFS Performance and Overhead Considerations

One of my favorite expressions is from a Heinlein novel: TANSTAAFL, which stands for "there ain't no such thing as a free lunch". What it means is simply that you usually don't get something for nothing. Life is full of tradeoffs, and certain costs that go with certain benefits. This is true of most things in life; it is true in the computer world in general, and it is also true of NTFS.

When it comes to NTFS, the tradeoff is generally between functionality and performance. NTFS has a lot of interesting and useful features and capabilities. However, most of these abilities come at the cost of overhead. The more options you add to a file system, the more disk space and processing is required to implement and manage them. This is simple common sense, but it is important to point out to those considering the use of NTFS. You can't expect to have a file system that allows flexible access control, compression, auditing, advanced reliability and other useful qualities without requiring the system to make some investments in allowing these features to work.

The performance implications of NTFS features mean that using NTFS may result in a slight decrease in performance compared to the use of a simpler file system such as FAT. Here are a few tips and issues to keep in mind when considering how to implement NTFS partitions, which may partially mitigate this performance impact:

• Use Only What You Need: Some of the fancier features in NTFS can impose more significant overhead penalties on the system than others, both in terms of processing power and the use of disk space. If you need those features, then in most cases they are worth the cost. However, it makes sense to avoid using features that you don't need. For example, don't compress frequently used files if you have lots of disk space; don't enable lots of audit logging unless you really require it, and so on.
• Use Adequate Hardware: Trying to implement a complex system on a low-powered system with a small, slow hard disk is probably asking for trouble. The overhead associated with NTFS becomes less and less noticeable on newer hardware (which is part of what is allowing Microsoft to add even more new features to the file system.)
• Watch The Cluster Size: While most people think of cluster size as being strictly a FAT file system issue, NTFS also uses clusters, and its performance is impacted by the choice of cluster size. Cluster size is in turn affected by the choice of partition size. In addition, under Windows NT the cluster size is different if the partition was converted from FAT. See here for a more thorough discussion of these issues.
• Fragmentation and Defragmentation: Contrary to a popular myth, NTFS partitions do become fragmented and performance can benefit from regular defragmenting. Windows 2000 comes with a defragmenter built into it; for Windows NT you will need to use a third-party tool.

It is wise to keep these performance issues in mind, both when using NTFS, and even in considering if you even want to use it. At the same time, you should not let these concerns "scare you off" from using NTFS. If you manage your system well and use reasonably modern hardware, the difference in performance between using NTFS and FAT partitions should not be a significant one. For a business, NTFS is pretty much indispensable, and if a bit more hardware needs to be thrown at the system to compensate for a small amount of overhead, it's usually an easy decision.

Note: For a more thorough, general discussion of hard disk performance, see this section.

Next: NTFS Partitioning Strategies

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