[ILUG] Mandrake 10

[Paul Jakma]

On Tue, 27 Apr 2004, Rick Moen wrote:

> Hmm, I'd have to look that up.  That was based on materials I have
> at home, before I left for the day.

There's a spec on serial-ata.org for port-multiplexing, presumably to
allow one to have intelligent backplanes that then just need only one
S-ATA connection to the host. (or even two, if the host/devices
support that pending multi-path spec).
 
> [Future doubling of theoretical SATA bus bandwidth limits]

You brought that one up.
 
> > Yeah, only way beyond SCSI. but hey.
 
> See, _right here_, this is the single most spectacular pons
> asinorum that ATA advocates get stuck on:  A theoretical bus speed
> limit is significant only if there's some prospect of ever being
> bottlenecked by it.

Did I say otherwise? Also, if you have a multiplexing SATA backplane,
the extra bandwidth _will_ be useful. No single drive may be able to
use 1.5GB/s, but 15 of them will get very close with todays high-end
drives.

Indeed, why exactly is it you never see SCSI buses with more than 4
devices on them, even though the bus can address 15 devices (+1
host), least not on any sane setups. Even U320, the absolute fastest,
could take 8 drives, at best, given not-too-fast drives before
suffering.

> Since ATA cannot support disconnected operation (only one device
> per chain can carry out operations at a time), 

This is irrelevant to SATA as it is point-to-point, except for the
case of multiplexing, see above. There is no other device on the link
to the host with which one could contend with, where disconnected
commands would help.

> saturate ATA/100.

What has ATA/100 got to do it with?

> Minor amounts of device-connection latency aside, there is thus
> _zero benefit_ from higher ATA bus-transfer speed ceilings, almost
> certainly for the medium future (2-3 years).

Who is talking about P-ATA? I wouldnt use P-ATA for multi-disk arrays
in a machine (unless each disk is behind its own SCSI bridge), I
wasnt suggesting such use either. Stop it.

> saturate the bus under real-world conditions.  And guess what?  It
> works.

Niall, care to step in? please.. :)

However, we were not discussing P-ATA, we were discussing S-ATA.  
S-ATA at last lets one attach multiple disks in a sane fashion.
 
> When U320 starts being obsolete, I'll be out there looking at what
> makes sense then for real computing.  Could be FC, could be
> Infiniband, could even be some outgrowth of IEEE-1394. 

Fibre Channel, yum. Insane for home use though. Good luck finding an
FC controller with linux support with anyway decent drivers.

> And I have no more time for what is clearly a fruitless discussion.

Absolutely, no small part due to your insistence on talking about 
P-ATA. Very annoying.

regards,
-- 
Paul Jakma	paul at clubi.ie	paul at jakma.org	Key ID: 64A2FF6A
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