NTFS Maximum Drive size?

[bjdobs]

Can anyone sight a reference for NTFS max hd sizes?
Specifically drives greater then 120G. I see mention that 137G is a limit (requiring a controller?)... if so are we back to partitioning large drives? Will drives larger then 120G even work properly on a EIDE controller (7200rpm)

 

[bcastner]

Under NTFS, the maximum size of a partition (volume) is in fact 2 to the 64th power. This is equal to 16 binary exabytes, or 18,446,744,073,709,551,616 bytes. (18 billion gigabytes).

 

[bjdobs]

Just found a link under MS ... XP implements a 2^32 max (even though the NTFS spec is 2^64) ... this still doesn't explain the Note for a Western Digital 160G HD stating that the MAX is 137M and that a card is required???

 

[bjdobs]

May be this is EIDE limitation???

IMPORTANT: Use Data Lifeguard Tools 10.0 or later installation software to access the full capacity of your hard drive. Hard drives larger than 137GB require a controller card to utilize full drive capacity.

 

[bcastner]

First, the 137 gig. is a difference in how the size of the drive is calculated.

Hard Drive manufacturers in general, define a gigabyte (abbreviated as GB) as 1 billion bytes (1,000,000,000 bytes).

Operating Systems and software utilities define a gigabyte as 1,073,741,824 bytes, which is based on an earlier way of measuring hard drive capacity. This method measures a kilobyte as 1,024 bytes rather than 1,000.

In like manner a megabyte is reported as having 1,024 X 1,024 bytes (1,048,576 bytes) rather than 1,000,000 bytes and a gigabyte as having 1,073,741,824 bytes.

Therefore a drive with a capacity of 9.1GB (or 9,100,000,000 bytes) on the label will have 7.37% less capacity when expressed in Gigabytes, 4.86% less capacity when expressed in Megabytes, or 2.4% less capacity when expressed in Kilobytes. For example:

9,100,000,000 decimal bytes divided by 1.048576 equals 8,678.436+ binary Kilobytes, equivalent to 8.67 MB.

Second, the recommendation for the new controller is because the drive is designed to run at ATA133, and most computers support ATA66 or ATA100. If your computer supports ATA133 and there are no BIOS issues with the drive size you do not need a new controller. You can run the ATA133 drive on slower ATA controllers, it is just that the drive does not work as fast as it was designed.

 

[bjdobs]

The 137G limit is a bios issue ... the wd 160G note just states that the you need a card (which ther are providing with this drive) on drives over 137G ... yes well aware of the 1024 game (This is a throw back to the bit bashing days of powers of 2)... and as you have stated the card/note can be ignored with an ata133 interface.

thanx for the info

 

[bcastner]

The ATA-5 Specification barrier
According to the ATA specification, any drive over 7.88GB (8.46 billion Bytes) is supposed to report its "geometry" as 16383/16/63 (C/H/S). Which enables old software to access the first 7.84 to 7.88GB of such a drive, using CHS addressing and the BIOS Int 13h system call. And while a P-CHS over 16383/16/63 can be used to access all the drive capacity-- up to the ATA-5 128GB limit-- that is not the recommended way to do so. Rather, LBA addressing should be used to access those larger capacity drives. (Or at least any partition that goes over the 7.88GB BIOS Int 13h CHS barrier.)

So, LBA uses a 28 bit binary number to specify the sector number on a drive. Thus:

228 = 268435455 Sectors

268435455 Sectors x 512 Bytes/Sector = 137438952960 Bytes

Resulting in the 128GB (137.4 billion Bytes) ATA-5 size limit.

The current ATA-6 specification provides a new (separate) 48-bit binary field, to specify the sector number on drives over 128GB. This in turn requires new controller hardware, and new drivers that support this additional 48-bit addressing.