Barracuda XT, Barracuda, Barracuda Green, DiamondMax and other desktop SATA and IDE drives

[arlesterc]

Is it possible to have two drives that are the same make and model - same LBA count - but they show up as different sizes in the OS e.g. Windows shows one as slightly smaller than the other?  

Possible that after Windows NTFS formatting two same model/same make drives out of the box  e.g. one as C and one as D they would show up as slightly different sizes?

[fzabkar]

Can you give us more specific information?

The answer to your question is yes, if the drive's user area has been reduced by means of a Host Protected Area (HPA).

See the following article:

http://en.wikipedia.org/wiki/Host_protected_area

Gigabyte's Xpress Recovery BIOS steals approximately 2000 sectors from the top end of the user area to store a backup copy of itself there. See the following threads for more info:

http://forums.seagate.com/stx/board/message?board.id=ata_drives&view=by_date_ascending&message.id=1706#M1706

http://forums.seagate.com/stx/board/message?board.id=ata_drives&message.id=15707#M15707

[arlesterc]

The question was specifically about Windows not any other OS. Within that area it was general.  I buy two drives - same make model, same 'theoretical' size as per specifications of the drives. I format drive 1 with Windows 2003 let's say to create a C drive and get a certain size in properties of the drive. I then format drive 2 with the same  Windows installation to create a D drive.  Is it possible that the two drives could be slightly different as far as Windows is concerned after the formatting?

[everrest]

If you formatted one as a primary partion and the other as data the primary partition may have added overhead.

[fzabkar · Accepted solution]

I don't know of any reason why the two partitions should not be identical, if you used identical partitioning and formatting procedures.

However, you could format one drive as a bootable drive, in which case it would have additional boot files such as the NTLDR.

You could also choose different numbers of sectors per cluster for each drive. In a FAT file system, this would result in a smaller File Access Table for the drive with the greater cluster size, which in turn would make slightly more space available for data. However, the average file would have a slack space equal to half the cluster size, which would mean that the drive with the larger clusters would eat up the available space slightly faster.

For example, a drive that was formatted with 16 sectors per cluster would require a minimum of 8KB to store a file that consisted of only 1 byte, whereas a drive with a cluster size of 8 sectors would use 4KB for the same file.

The average file in the former case would waste about 4KB, while the wastage in the latter case would be only 2KB.