OT: Is any hard disk brand better/worse than the others?
lsorense-1wCw9BSqJbv44Nm34jS7GywD8/FfD2ys at public.gmane.org
Thu Dec 4 20:32:50 UTC 2008
On Thu, Dec 04, 2008 at 03:03:17PM -0500, jemcinto-cpI+UMyWUv+w5LPnMra/2Q at public.gmane.org wrote:
> D. Hugh Redelmeier <hugh-pmF8o41NoarQT0dZR+AlfA at public.gmane.org>:
> > | From: jemcinto-cpI+UMyWUv+w5LPnMra/2Q at public.gmane.org
> > | > Ehm, DOS style partition table has a limit of 2TB (2^32 sectors).
> > |
> > | 2^32 sectors is NOT 2TB, it is 4GB.
> > ???
> > 2^32 = 4G
> > A sector is (usually) 512 bytes so
> > 2^32 sectors = 2TB
> I apologize. You are correct.
> On the other hand, MS-DOS prior to MS Windows 95 supported only 2 GB per
> Did it use only 22 bits of the 32 ?
FAT16 used a signed (unsigned on windows NT) 16bit cluster count, with a
maximum cluster size of 64k, which meant you could have at most
32768*64K in a single filesystem. Hence 2GB.
FAT32 (win98 and I think Win95OEM2) uses 32bit values and hence can have
much larger cluster count and at the same time use more sane cluster
sizes. Allocating in increments of 64k was not very efficient since on
average you waste 32k per file for large files, and for small files you
often waste almost 64k per file on the disk.
So the 2GB limit was a partition size limit due to the filesystem
limitations, nothing to do with partition table limitations (which is
what the 2TB limit is).
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