Re: Big files in ext2fs (but not i_osync)

H. Peter Anvin (hpa@transmeta.com)
3 Mar 1998 16:04:50 GMT

Followup to: <199803031220.HAA18793@saturn.cs.uml.edu>
By author: "Albert D. Cahalan" <acahalan@cs.uml.edu>
In newsgroup: linux.dev.kernel
>
> > Maybe, but it does not allow any form of sparse files!
>
> Sure it does, since you can always revert to traditional ext2
> as soon as some broken software tries to make a sparse file.
> If extents already exist, the remaining ones get filled in with
> one-block references to block 0.
>
> A file with 1 block at a random location is never going to be
> faster than a file with 1 block at the beginning, and it will
> always be slower on traditional unix filesystems like ext2.
> I think sparse files are a hack related to a.out binary format
> and obsolete database libraries.
>

<FLAME>

Albert, you think any feature you don't personally use is a waste and
obsolete! I'm sorry for the observation, but I can't shut up about
this anymore...

</FLAME>

The capability for handling sparse files is quite powerful, and when
you are talking about databases or other aggregate file types it is a
very useful feature, especially for stuff you want to mmap().

A problem with it in its current configuration is the lack of a
punch() system call that can be used to hole out unused blocks, but to
say that sparse files are broken and obsolete is nothing but crap.

-hpa

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