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SubjectRe: IDE hotplug support?
On Thu, 2 May 2002, Jakob Østergaard wrote:

> 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...

I was doing some testing on a Compaq ProLiant 380 (perhaps G2 - don't
remember) that was doing some 70-80MB/s on a RAID-5. That was, however, on
12 drives, 6 on each a controller. I managed to do a little more with JBOD
and Linux Software RAID-5. That said, this was 18GB drives, which aren't
the fastest drives on earth...

roy

--
Roy Sigurd Karlsbakk, Datavaktmester

Computers are like air conditioners.
They stop working when you open Windows.

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