Size and Size on disk question

[Guest]

Hi all,

I have a Win2K server. It’s C: drive is in FAT.

When I go to C:\WINNT properties, it shows the Size is 1.81 GB and Size on
disk is 2.69 GB.

Could you tell me the difference between Size and Size on disk? 2.69 GB
seems to be the actual disk space used, right?

On another Win2K servers which has NTFS on its C: drive, the Size on disk is
greater than Size. This is confusing. ïŠ

Is this because of FAT and NTFS file system issue?

Thanks.

Abel Chan

 

[Bruce Chambers]

Hi all,

I have a Win2K server. It’s C: drive is in FAT.

When I go to C:\WINNT properties, it shows the Size is 1.81 GB and Size on
disk is 2.69 GB.

Could you tell me the difference between Size and Size on disk? 2.69 GB
seems to be the actual disk space used, right?

"Size" refers to the actual total of the sizes of all of the individual
file sizes, while "Size on Disk" refers to the total amount of disk
space occupied by those files. The difference is because some of the
files do not occupy an entire cluster. For instance, a 1 Kb file is
occupying a single 4 Kb (or 8 Kb or 16 KB) cluster. Clusters cannot be
shared by different files, so there will always be some wasted space
whenever a file doesn't completely fill a cluster. If there are a lot
of small files, the wastage becomes quite noticeable.

You've said that the partition is using the FAT file system, but I
assume that you meant FAST32, as FAT partitions are very limited in
size. While FAT32 allows much larger partitions, it is still quite
wasteful of space, if the partition exceeds 8 Gb in size. This is due
to FAT32's designed cluster sizes:

Volume Size FAT16 FAT32 NTFS
Cluster Size Cluster Size Cluster Size
2 GB–4 GB 64 KB 4 KB 4 KB
4 GB–8 GB Not supported 4 KB 4 KB
8 GB–16 GB Not supported 8 KB 4 KB
16 GB–32 GB Not supported 16 KB 4 KB
32 GB–2 terabytes Not supported 32 KB? 4 KB

So, on a modern hard drive with large partitions, you can see how a
small file can easily "consume" a great deal of disk space. The same
thing occurs on an NTFS partition, of course, but to a much small
extent, due to NTFS's smaller cluster size.




--

Bruce Chambers

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[Colon Terminus]

Hi all,

I have a Win2K server. It's C: drive is in FAT.

When I go to C:\WINNT properties, it shows the Size is 1.81 GB and Size on
disk is 2.69 GB.

Could you tell me the difference between Size and Size on disk? 2.69 GB
seems to be the actual disk space used, right?

On another Win2K servers which has NTFS on its C: drive, the Size on disk is
greater than Size. This is confusing. ?

Is this because of FAT and NTFS file system issue?

Thanks.

Abel Chan

That's because the smallest amount of data that can be written to the disk
is 1 "cluster". Size on disk is always going to be larger than Size unless
Size is an exact multiple of cluster size in which case they'll be
identical.

See this article for how default cluster size is determined:
http://support.microsoft.com/default.aspx?scid=kb;en-us;140365

See this article to see how to find out your cluster size(s):
http://support.microsoft.com/default.aspx?scid=kb;en-us;245436

 

[Guest]

Thanks so much Bruce for the detail explanation and the size reference.

Sincerely,

Abel

 

[Guest]

Thanks Colon.

Abel

That's because the smallest amount of data that can be written to the disk
is 1 "cluster". Size on disk is always going to be larger than Size unless
Size is an exact multiple of cluster size in which case they'll be
identical.

See this article for how default cluster size is determined:
http://support.microsoft.com/default.aspx?scid=kb;en-us;140365

See this article to see how to find out your cluster size(s):
http://support.microsoft.com/default.aspx?scid=kb;en-us;245436