FAT real disk usage
leibnizster
using FAT (32 but please explain the differences if any)?
Of course files occupy an integer number of cluster sizes (512B, 4KB
or whatever the drive is formatted as). Besides these are there other
structures used that take additional space (dynamically created)? And
how much space does a directory take? Does it depend on the number of
files it has underneath? Does it have data outside the FAT? I read
some FAT specs but did not quite get this issues. Thank you.
mscot...@aol.com
All files are directories are part of the FAT system. The only area
outside of the FAT is the FAT itself, plus a few boot and BIOS sectors
A typical cluster size on FAT disks is 16K. This means that any file
between 1 byte and 16K will occupy 16K of the disk.
A directory entry is always at least 32 bytes, and for long file names
this will increase by increments of 32 bytes. Again the minimum size
of a directory cluster will be typically 16K.
For a disk with many small fies, the use of the disk is very poor.
For a disk with a few large files, the useage is much better, though
there is a 4GB limit on the maximum size of a FAT32 file
Michael
www.cnwrecovery.com
leibnizster
So, a directory can occupy more than one cluster? What does this
depend on? And for the directory table, is there a maximum number of
characters allowed? Thank you.
Tim Slattery
>So, a directory can occupy more than one cluster?
Yes
> What does this depend on?
Just like any file, it depends on how much data needs to be stored.
When one cluster is filled, another will be allocated.
> And for the directory table, is there a maximum number of
>characters allowed? Thank you.
Directories are filled with entries. A directory entry (in FAT32) is
32 bytes. Each file will take at least one entry, and files with names
that don't fit the DOS 8.3 mold will take from two to thirteen
entries, depending on the length of the name.
For complete details, see the FAT32 specification at
http://www.microsoft.com/whdc/system/platform/firmware/fatgen.mspx
--
Tim Slattery
MS MVP(Shell/User)
Slatt...@bls.gov
http://members.cox.net/slatteryt
leibnizster
> Just like any file, it depends on how much data needs to be stored.
> When one cluster is filled, another will be allocated.
When is one cluster filled? When it holds too many entries? How does
one compute the number of clusters it occupies if one knows the number
of entries (subfolders and files) that it has?
Tim Slattery
>On Mar 12, 2:45 pm, Tim Slattery <Slatter...@bls.gov> wrote:
>> Just like any file, it depends on how much data needs to be stored.
>> When one cluster is filled, another will be allocated.
>
>When is one cluster filled? When it holds too many entries?
Yes, when you need to add another entry and there's no room for it.
> How does
>one compute the number of clusters it occupies if one knows the number
>of entries (subfolders and files) that it has?
Divide cluster size by 32 to find out how many entries fit into a
cluster. Divide total number of entries by that number.
Total number of entries is not going to be easy to determine. As I
said before, each file or subfolder takes from one to thirteen
entries, depending on name length.
Stretch
news:e1eaef05-bf04-4650...@s12g2000prg.googlegroups.com
> > How much real disk space do files and folders take on a hard drives
> > using FAT (32 but please explain the differences if any)?
> >
> > Of course files occupy an integer number of cluster sizes (512B, 4KB
> > or whatever the drive is formatted as). Besides these are there other
> > structures used that take additional space (dynamically created)? And
> > how much space does a directory take? Does it depend on the number of
> > files it has underneath? Does it have data outside the FAT? I read
> > some FAT specs but did not quite get this issues. Thank you.
> All files are directories are part of the FAT system. The only area
> outside of the FAT is the FAT itself, plus a few boot and BIOS sectors
Bwahaha.