RoofingGuy wrote:
There’s a difference between the size of the physical sectors on the drive and the size of the Allocation Units that Windoze uses when formatting – one is dependent on Windows and one is dependent on the drive.
On a non-Advanced Format drive, it doesn’t matter what Allocation size is chosen, whether it’s 512, 1024, 2048, 4096, 8192, 16384, 32768, 65536… the drive still uses 512-byte physical sectors to store those units… it’s just that it uses 1, 2, 4, 8, 16, 32, 64, 128… physical sectors of disk space to contain each Allocation Unit.
The Allocation Unit just controls the minimum size that Windoze will devote to each file. It will allocate a whole number of Allocation Units (and the equivalent number of physical sectors) to each file. No bits of another file can be stored in the unused space. So your drive “wastes” an average of half an allocation unit per file on the drive.
The fact that Windows has problems with allocation tables that use 512-byte allocation units once you hit 2TB has nothing to do with whether the drive has 512-byte physical sectors or 4k physical sectors.
The drive can only hold 2^32 entries in the Allocation Table under NTFS. At 512 bytes per allocation entry, there is no space in the allocation table for any entries past 2TB. If you managed to format a drive with 512-byte Allocation Units, the FAT can only index the first 2TB of space. Using larger Allocation Units allows you to access a larger space from the same size of Allocation Table.
So yes, with 4k physical sectors on the disk, it will presumably be necessary to use Allocation Units that are a multiple of 4k, and not multiples of 512, so that each Allocation unit is a whole number of physical sectors, but on non-AF disks, they’ve always used 512-byte physical sectors no matter what size Allocation Unit was used for formatting.
Thank you!! =D
