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Cluster size default gets an adjustment

Changing your cluster size in Windows Server 2003 could improve performance, but you need to evaluate current and future file sizes before you do this.

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Although the default cluster size in Windows Server 2003 NTFS file system is well chosen for average applications, you can improve efficiency for some uses by changing the default.

But keep in mind that if you choose to do this, you need to be familiar with the present and likely future file sizes

Here are a few general guidelines to contemplate as you decide what your cluster size should be.

Should cluster size match smaller files?
In volumes over 3 GB the NTFS cluster size is set to 4K. If the files are usually 4K or less, Microsoft recommends leaving the cluster size alone. Although you might increase theoretical efficiency by reducing the cluster size to match smaller files, you will also increase fragmentation, especially if the files grow to fill more than one cluster.

If the files tend to be large and will probably get larger, Microsoft recommends using 16K or 32K clusters if you do not intend to use NTFS compression.

If you use shadow copy to make point in time copies of the volume for data protection and you plan to defragment the volume, Microsoft recommends using a cluster size of at least 16K. Otherwise, the changes caused by defragmentation can cause shadow copies to be deleted faster than expected.

Microsoft discusses these issues in the Windows Server Deployment Guide. Available on the Microsoft website, the specific URL for this section is:

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Rick Cook has been writing about mass storage since the days when the term meant an 80K floppy disk. The computers he learned on used ferrite cores and magnetic drums. For the last 20 years he has been a freelance writer specializing in storage and other computer issues.
This was last published in February 2005

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