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March 27th, 2004 18:00
How to chose the correct cluster size?
Hello,
The following table shows the default values that Windows XP uses for NTFS formatting.
Drive size
(logical volume) Cluster size Sectors
----------------------------------------------------------
512 MB or less 512 bytes 1
513 MB - 1,024 MB (1 GB) 1,024 bytes (1 KB) 2
1,025 MB - 2,048 MB (2 GB) 2,048 bytes (2 KB) 4
2,049 MB and larger 4,096 bytes (4 KB) 8
I'm in the process of reformatting my E partition (approx. 4 GB) (basically to delete
existing files and create a storage area) and I can chose an allocation unit size
or chose default which is the largest, see 4KB above. Which is best; the reason I
ask the question is that in a product information message they state that small clusters
are better. How does one chose? I plan to use the storage for My Documents. Thanks.
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JRosenfeld
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March 27th, 2004 22:00
The cluster size is really only important if you have a lot of very small files, since a file smaller than the cluster size uses up the whole cluster and so wastes disk space. This was a problem in FAT formats, where the minimum cluster size became very large for large partitions, but with NTFS and largest cluster size only 4KB, on an average setup most files are much larger than 4KB, the overall disk space wasted is therefore very small.
Example: if I click on properties on, say, C:\program files, it shows 45194 files, total 4,087,068,238 bytes, disk space used 4,182,958,080 bytes, i.e. 2.5% larger. On my old PC with windows 98, on a large partition (cluster size 128KB, I think, the waste was much bigger, up to about 15% for a comparable example
If you have mostly very large files (e.g. video), some people recommend larger cluster size.
Personally, I would stick to the default.
See also
http://www.experts-exchange.com/Storage/Q_20795143.html
and
http://www.pcguide.com/ref/hdd/file/ntfs/impl_Part.htm and other links on that site.