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Windows File System clusters explained
Wasted Space Explained
Wasted space is a "per file" basis, as each cluster can only store 1 file, so if this file takes up 10 clusters, there will only be wasted space from the leftover of the last cluster. If you have a file that is exactly 32KB * X then there is 0 wasted space. Also, if you were to cut your big video files in many small parts, it would waste more then if you combined all your videos into one large file. I'm not telling you to combine all your files into one, but one thing for sure, if you have lot of file archives you wont use in years, zip it up as one file and not only will you save space from compression, but you will also save space because only 1 cluster will be left with wasted space left over - up to 32KB of wasted space.

Finding out the size of your clusters
If you are curious to know the size of the clusters on your drive, you can use an utility like Partition Magic or you can check it yourself by creating a file (at least 1 byte) and checking its properties. Where it says "size on disk" you should see something like 32KB. This is also useful to see how much space large files take up. For example, a 892 312 048 byte file will actually be taking up 892 338 176 bytes of disk space. If you calculate 892 338 176 ? 892 312 048 you will notice that 26 128 bytes are wasted, which is about 26KB. This is not that bad to consider that it's a 850MB file to start off with anyway, but when you have many small files (ex: cookies) the amount is huge compared to the actual file size and there is more wasted space because of so many individual files wasting up to 32KB in space each. So empty your cookies once in a while!

A better file system: NTFS
There is another newer file system called NTFS(New Technology File System), which is way more efficient than FAT. NTFS is much better than FAT, but is not compatible with windows 3.x/95/98/ME or DOS, but compatible with Windows XP, 2000 and NT. Use it whenever possible. It has many options such as:

  • Logging and mapping in case of failure, makes recovery much easier and more possible.
  • Maps out bad sectors to make sure they are never used.
  • Security features such as possibility to encrypt/decrypt data as it is written/read from the disk. This would make raw reading next to impossible, so files are more secure when you give your HD to someone else.
  • Possibility to set user permissions (kind of like chmod in linux/unix).
  • Using only 4KB clusters, it can support a partition of up to 16TB and a partition of up to 256TB using 64KB clusters!
  • Possibility to have built-in(controlled by the file system and not the actual sharing application) disk quotas for shared drives.
  • Possibility to compress without another program such as Ms disk compression. Other Windows applications can read/write without having to know the partition is compressed.

    Not only does NTFS have more built-in features, but it has practically no limits (who owns a 256TB drive and want to keep it as one partition?!) and also has very small cluster sizes. A partition that would use 32KB clusters would only use like 2KB or 4KB clusters in NTFS! However, NTFS is only compatible with Win2k/XP/NT, so you would not be able to change files on an NTFS partition unless you are in one of those operating systems. You could always use FAT32 for those, but why do that?


    I hope that this article helped you understand the concept of clusters better. If you have comments or suggestions please don't be shy and use the feature below, and also consider joining our forum for great discussions on tech-related issues and off topic stuff as well!

    This article originally for IceTeks.com


  • Written By: Red Squirrel
    Date: 4-11-04
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