Re: atomicity

H. Peter Anvin (hpa@transmeta.com)
7 Dec 1998 19:55:43 GMT

Followup to: <m3soeszi1e.fsf@trantor.cosmic.com>
By author: Mirian Crzig Lennox <mirian@xensei.com>
In newsgroup: linux.dev.kernel
>
> alan@lxorguk.ukuu.org.uk (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.
>

Actually, ext2fs uses *block groups*. It aligns them on a number of
blocks that's a power of 2 (usually 2^13 blocks); not on a "cylinder" boundary.

-hpa

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