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NTFS true maximum partition size

Posted on 1998-12-15
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According to microsoft, for NTFS "The maximum partition size is 2TB (terabyte, a trillion bytes). NTFS actually has an upper limit of 16 exabytes (quintillion bytes, or 16 million TB), but since current industry standard limits the Partition Tables to 2 to the 32nd power sectors (with 512B sectors, that's 2 TB), the actual current upper limit is 2 TB."

BUT I have often heard, (even at EE), that the actual maximum size for a single parition is around 5 GB? Is this true? Or is it that due to some hardware limitation that it is impossible map more than this? In a nutshell if I have, say, a 10GB hard disk. Can I have a single 10 GB NTFS partition. And if not, why not?
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Question by:arunm
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12 Comments
 
LVL 7

Expert Comment

by:BlackMan
ID: 1796053
We have a partition on 650 GB, so 10 GB should cause you no problems, as far as NT is concerned.
There might be some problems with your BIOS/Diskcontroller and there is a max of 4 GB for the boot partition (see http://support.microsoft.com/support/ntserver/serviceware/10140753.ASP)

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Expert Comment

by:Lee W, MVP
ID: 1796054
While I don't remember the specifics, I believe that the Boot Partition must be 8GB or less.  Any other partitions can be any size up to the theoretical maximum.
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Expert Comment

by:BlackMan
ID: 1796055
leew, the Boot Partition can be a max of 4 GB because NT Setup treat it as a FAT partition. For more details, check the article in my answer
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LVL 5

Expert Comment

by:carmine
ID: 1796056
The *general* max size for the boot partition is 7.8GB (BIOS Int13 limitation) but this cannot be created by NT setup which is limited to creating 4GB partitions (NT FAT limitation).

To achieve the 7.8GB you have to use NTFS, and precreate the partition on the disk by formating it under another NT instance.

(*general* because this assumes Intel and not Alpha, and some SCSI adapters can get round this limitation.)
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Author Comment

by:arunm
ID: 1796057
It appears we are on the right track here. Im still unclear about the extent of bios / disk controller limitation. Can you Elaborate? Which bioses does this effect?
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Expert Comment

by:carmine
ID: 1796058
To clarify are you interested in boot/system partitions, or partitions in general?
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Author Comment

by:arunm
ID: 1796059
Sorry if im wasn't clear enough. As in the original question, im interested in the general limitations placed on the maximim size of a NTFS partition. ( we are talking "pc's" here).
If there are hardware restrictions to this size, im curious to what they are.

 
 

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Expert Comment

by:carmine
ID: 1796060
For partitions other than the boot/system, your original comment sums up the situation pretty well.

For Intel boxes there is an adittional limitation. This is caused by the BIOS on the motherboard.  This uses Int13 to access the disk/partition it is to boot from.  The Int13 data structures for disk geometry limit the max usable partition size to 7.8GB.  Any larger than this and you'll probably get a 'disk not found' message.

Once the boot code on the disk has loaded the NT OS via the NT Loader, the BIOS Int13 is no longer used and we get into Terrabyte territory.

I can root out the Int13 structures if you like.
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Expert Comment

by:carmine
ID: 1796061
More info on booting from TechNet:

On x86-based computers, the Starting and Ending Head, Cylinder, and Sector fields on the startup disk are very important for starting up the computer. The code in the Master Boot Record uses these fields to find and load the Partition Boot Sector.
The Ending Cylinder field in the Partition Table is ten bits long, which limits the maximum cylinder number that can be described in the Partition Table to 1023. The Starting and Ending Head fields are one byte long, which limits this field to the range 0 – 255. The Starting and Ending Sector field is 6 bits long, limiting its range to 0 – 63. However, sectors start counting at 1 (versus 0 for the other fields), so the maximum number of sectors per track is 63.

Since current hard disks are low-level formatted with the industry standard 512-byte sector size, the maximum capacity disk that can be described by the Partition Table can be calculated as follows:
MaxCapacity = (sector size) x (sectors per track) x (cylinders) x (heads)
Substituting the maximum possible values yields:
512 x 63 x 1024 x 256 = 8,455,716,864 bytes or 7.8 GB (GB)

This calculation results in a maximum formatted capacity is slightly less than 8 GB.

However, the maximum cluster size that you can use for FAT volumes when running Windows NT is 64K, when using a 512 byte sector size. Therefore, the maximum size for a FAT volume is 4 GB.

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Author Comment

by:arunm
ID: 1796062
Thanks blackman. But carmine's answer was a little better, even though you did address the question. Carmine can you repost as an answer.

 
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Accepted Solution

by:
carmine earned 200 total points
ID: 1796063

For partitions other than the boot/system, your original comment sums up the situation pretty well.

For Intel boxes there is an adittional limitation. This is caused by the BIOS on the motherboard.  This uses Int13 to access the disk/partition it is to boot from.  The Int13 data structures for disk geometry limit the max usable partition size to 7.8GB.  Any larger than this and you'll probably get a 'disk not found' type message.

Once the boot code on the disk has loaded the NT OS via the NT Loader, the BIOS Int13 is no longer used and we get into Terrabyte territory.
 
 
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Expert Comment

by:jnkyrd111
ID: 1796064
The actual boot partition size is 4096MB.
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