[hfs-user] HFS Maximum Image Size

Mark Day mday@apple.com
Mon, 22 Apr 2002 13:35:56 -0700


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The maximum file size on HFS volumes is 2GB-1 (the maximum value in a=20
signed 32-bit integer).  See struct HFSCatalogFile.

The maximum volume size is theoretically just under 256TB (actually,=20
65535 allocation blocks * (4G-512) bytes per allocation block).   The=20
allocation block size is an unsigned 32-bit integer, but must be a=20
multiple of 512.  I don't know of any implementation that supports HFS=20=

volumes 2TB or larger; some versions have much smaller limits (eg., 2GB=20=

or 4GB).  Many implementations use 32-bit integers (signed or unsigned)=20=

for offsets into the volume, or as block numbers (assuming 512 bytes per=20=

block).

-Mark

On Sunday, April 21, 2002, at 07:44 AM, Entwicklung wrote:

> =A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0 The maximum =
size of an HFS-volume seems to be=20
> 65535*65535 =3D 3.99 GB. (since the respective fields in the MDB are=20=

> UInt16's). Does this mean that to store a=A0file of size=A04.7GB I =
would=20
> have to necessarily go in for HFS+ or is this possible with=20
> HFS=A0somehow ?

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The maximum file size on HFS volumes is 2GB-1 (the maximum value in a
signed 32-bit integer).  See struct HFSCatalogFile.


The maximum volume size is theoretically just under 256TB (actually,
65535 allocation blocks * (4G-512) bytes per allocation block).   The
allocation block size is an unsigned 32-bit integer, but must be a
multiple of 512.  I don't know of any implementation that supports HFS
volumes 2TB or larger; some versions have much smaller limits (eg.,
2GB or 4GB).  Many implementations use 32-bit integers (signed or
unsigned) for offsets into the volume, or as block numbers (assuming
512 bytes per block).


-Mark


On Sunday, April 21, 2002, at 07:44 AM, Entwicklung wrote:


<excerpt><fontfamily><param>Arial</param><smaller>=A0=A0=A0=A0=A0=A0=A0=A0=
=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0
The maximum size of an HFS-volume seems to be 65535*65535 =3D 3.99 GB.
(since the respective fields in the MDB are UInt16's). Does this mean
that to store a=A0file of size=A04.7GB I would have to necessarily go in
for HFS+ or is this possible with HFS=A0somehow ?</smaller></fontfamily>

</excerpt>=

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