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SubjectRe: SCSI tape blocks > 128k ?
On Aug 25, Alan Cox wrote:

> > http://samba.anu.edu.au/cgi-bin/linux-patches/incoming?id=267
> >
> > The patch implements the bigbuffer support required for this use, and
> > patches "sg" to actually use it. A two-line patch will allow st to
> > also use this......
>
> Its a workable answer, but not the right one. The right one is to propogate
> the use of scatter gather better and eventually (2.3.x I hope) DMA to
> user pages. Modern SCSI controllers dont need 1Mbyte of linear memory
> for this. And non DMA old ones are generally sufficiently dumb you can
> implement scatter gather in the cpu driven byte copy routines

but at least my setup is just in the middle of these two extremes:
the DAT is connected to a good old AHA1542B (it's only for external devices
which can be hot-plughed without risk; I don't need to touch the SCSI bus
for faster disks), so I need DMA and can't use scatter gather (AFAIK)...

having bigbuffer support addtional to a better scatter gather method
for more recent hardware would be the best thing[tm] (and that's what Linux
is trying to be, isn't it?;)


Harald
--
All SCSI disks will from now on ___ _____
be required to send an email notice 0--,| /OOOOOOO\
24 hours prior to complete hardware failure! <_/ / /OOOOOOOOOOO\
\ \/OOOOOOOOOOOOOOO\
\ OOOOOOOOOOOOOOOOO|//
Harald Koenig, \/\/\/\/\/\/\/\/\/
Inst.f.Theoret.Astrophysik // / \\ \
koenig@tat.physik.uni-tuebingen.de ^^^^^ ^^^^^

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