FAT32 confusion... (size limit vs cluster limit)

[Red Squirrel]

I've been doing research on how FAT 12, 16 and 32 differ as I'm writting an article on clusters and I will go into details into why there are limits. I learned that FAT32 is actually 28 bits, so that gives it a maximum of 268435456, and the biggest cluster size for FAT32 is 32KB, so if I do 268435456 times 32KB it gives me 8796093022208 bytes, which is 8TB, but the limit is known to be 2TB. Can someone explain what I'm doing wrong here? I know the 4 bits "left" are reserved which is why it's still called fat32, but is there any other reserved stuff that I'm missing? I want to make sure my article that I will write will be right, and want to go further then just slaping on what I found on the net.

Thanks

 

[Red Squirrel]

Bump!

Wow this forum moves fast. I've been hanging out at the 50-member boards a little too much, maybe.

 

[DaveSimmons]

Have you checked the FAQ on the main AT site, and the microsoft.com tech refs?

 

[Whitedog]

Yes, TechNet has an artical explaining everything you're asking... and then some. I've read it before. Go search for it (FAT32).

Are you writing an artical about it for the web? Save yourself some time and just put a link to the MS artical.

 

[Red Squirrel]

Yeah, I'm writting an article for my site (http://www.iceteks.com) so I can add to my huge database of 21. lol

Some site (bitbendertech) has this thing against me and wants to compete, so I'm writting articles on every subject I can think of. I have one coming soon, it will be a tour of a telcommunication facility. Should be quite interesting. When I mention DE-4 people will then know how it looks like.

I just found the one at Ms, no time to read it now but if I need more help I'll post here, I'm sure a bit more research should get me there.

 

[AndyHui]

Read this.

 

[Pariah]

There probably isn't any reason for the 2TB limit beyond practicality. The FAT for a 2TB partition would be 256MB with 32KB clusters, which is already pretty unwieldy, now quadruple that for 8TB and you end up with a ridiculous FAT of 1GB. Trying to cache a 1GB FAT in system memory would cause some problems to say the least. With the move to NTFS and the elimination of FAT based files sytems, this problem should never become an issue. The official limit is 2TB, but there are probably other barriers that will be reached before we get there, if we ever do.

 

[Red Squirrel]

Oh ok, so my calculation is right than, it's just that it would be unefficient to use 8TB with fat32. Thanks for clearing that up. That will be something interesting to add in my article, that it's actually 8TB but that it would be unefficient and not recomended (and does not yet exist , well maybe server raids but that's Linux)