"H. Peter Anvin" wrote:
>
> Followup to: <38EE3F9F.58C82CA0@timpanogas.com>
> By author: "Jeff V. Merkey" <jmerkey@timpanogas.com>
> In newsgroup: linux.dev.kernel
> >
>
> Have you considered using the md device or something similar as an
> intermediate layer? That way you get a single linear descriptor
> across all the partitions.
>
> It's not that "Linux always seems to assume that..."; rather, far too
> often it's that Linux doesn't do things the way you seem to expect
> them too. You should have noticed that by now.
No, it does what I would expect a unix OS to do, including both the good
and bad things about Unit. It's very similiar (though not identical) to
the other Unixes, but with more of a PC flair.
>
The md device layer simply expands the "one partition - one filesystem"
concept by saying. " ... here's a bunch of partitions that look like
"one partition - one filesystem". This won't work with NetWare's
segmentation model since volume segments are something the FS needs to
know about. It could work this way in Linux with the mirroring (NetWare
mirroring could be made to work with the current md architecture, but
not without significant rework of the buffer cache to support logical
rather than physical block mapping). Striping, however, is a different
matter and I need to give this some thought. We could use the md
devices to do it by concatenating NetWare partitions together, and
telling all volumes they are only on one segment (and use md underneath
to remap the partitions) but such a scheme would not be as efficient for
stiping as what's currently there. Since the FS knows about segments,
we simply round robin cluster allocation requests between segments, and
get very good fie distribution across multi-segmented volumes. Using md
to do this would not be as good since the FS would simply allocated
until it spanned into the next partition -- NTFS model -- not as good as
what's already there.
Jeff
> -hpa
> --
> <hpa@transmeta.com> at work, <hpa@zytor.com> in private!
> "Unix gives you enough rope to shoot yourself in the foot."
>
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