Re: atomicity

Horst von Brand (
Mon, 07 Dec 1998 12:10:42 -0300

Mirian Crzig Lennox <> said:
> (Alan Cox) writes:

> > ext2fs tries to grab linear chunks of disk and divides the disk into
> > cylinder groups to also help to maintain locality. The BSD ffs papers
> > [McKusik et al] describe this sort of stuff well.

> I am astonished to hear that ext2fs uses cyl groups.

> I was of the impression that these were an artefact of ffs, and really
> not useful anymore. With modern disks, chances are excellent that the
> specific 3D geometry the file system sees is an utter fiction, and
> that cylinder locality is thus more-or-less a meaningless concept.

It is a meaningless as such, but block locality is important anyway. And
"cylinder groups" are an approximation to that.

Dr. Horst H. von Brand             
Departamento de Informatica                     Fono: +56 32 654431
Universidad Tecnica Federico Santa Maria              +56 32 654239
Casilla 110-V, Valparaiso, Chile                Fax:  +56 32 797513

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