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SubjectRe: IDE hotplug support?
On Thu, May 02, 2002 at 09:26:38PM +0100, Alan Cox wrote:
> > >=20
> > > 8 x 130MBy/s >>>> PCI bus throughput... I would rather recommend
> > > a classical RAID controller card for this kind of
> > > setup.
> >
> > Because RAID controllers do not use the PCI bus ??? ;)
>
> The raid card transfers the data once, software raid once per device for
> Raid 1/5 - thats a killer.

For RAID-1 it's a killer (for writes), I agree.

But I really doubt it would be so horrible for RAID-5 - after all, it's only
one extra block (the parity block) for each N-1 blocks written (for an N disk
RAID-5). The penalty should be less, the more disks you have in the array.

But seriously, has anyone out there ever seen a hardware RAID controller with
a *sustained* RAID-5 thoughput of more than 60 MB/sec ? Not that I think it
is impossible, but I've never heard about it. Enlighten me, please, and not
with marketing numbers...

>
> > By the way, has anyone tried such larger multi-controller setups, and t=
> > ested
> > the bandwidth in configurations with multiple PCI busses on the board, =
> > versus a
> > single PCI bus ?
>
> With 2.4 yes. With all the 2.5 changes no.

Did you get any speedup ? Were you close to PCI bus saturation in the one-bus
scenario ?

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