[TUHS] Unix filesystem semantics history - files with holes

William Corcoran wlc at jctaylor.com
Fri Apr 12 05:09:47 AEST 2019

Sparse files: “Thin Provisioning” way ahead of its time.  Combined with the patented SUID: The UNIX marvels never cease.  

It just goes to show that all this marketing BS touted today has already been done before.  

Bill Corcoran 

On Apr 11, 2019, at 12:36 PM, Richard Tobin <richard at inf.ed.ac.uk> wrote:

>> When did the Unix filesystem add the semantics for "files with holes" (large,
>> sparse files)?
> It was there in the first edition:
> https://www.bell-labs.com/usr/dmr/www/pdfs/man51.pdf
> The FILE SYSTEM (V) man page includes a last paragraph identical to
> that of FILSYS (V) in seventh edition:
>  If block b in a file exists, it is not necessary that all blocks
>  less than b exist.  A zero block number either in the address words
>  of the the i-node or in an indirect block indicates that the
>  corresponding block has never been allocated.  Such a missing block
>  reads as if it contained all zero words.
> The first edition indirect blocks were a bit different though: if the
> file was bigger than 8 blocks (4kB), all the blocks in the inode were
> (singly) indirect.
> -- Richard
> -- 
> The University of Edinburgh is a charitable body, registered in
> Scotland, with registration number SC005336.

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