msdosfs vs 250Gb hard disk

David Schultz das at FreeBSD.ORG
Fri May 2 04:24:19 PDT 2003

On Sat, Apr 26, 2003, Daniel O'Connor wrote:
> I am attempting to utilise a 250Gb Maxtor external Firewire drive. To
> obtain maximum portability I would prefer to format it as FAT32 (it comes
> formatted that way) - that way Windows, Linux and FreeBSD machines can
> access it.
> Unfortunately FreeBSD doesn't grok really large FAT32 partitions :( When I
> attempt to mount it, I get ->
> mountmsdosfs(): disk too big, sorry

Most filesystems have a unique identifier associated with every
file, but msdosfs does not.  The FreeBSD driver invents inumbers
on the fly as the index of the directory entry for the file,
assuming that the entire disk is full of directory entries.  These
numbers are 32 bits and they need to be persistent, so it would
not be possible to play any clever tricks with the math.

I suggest that you ensure that all of your FAT32 filesystems are
smaller than 128GB (2^32 * 32 bytes/direntry).  Note that msdosfs
performance and reliability generally sucks, so unless you're
using the disk merely as a buffer to transfer stuff between
operating systems, you probably want to rethink your decision.

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