Re: IDE hotplug support?

["Jakob Østergaard" <jakob@unthought.net>]

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 ?

-- 
................................................................
:   jakob@unthought.net   : And I see the elder races,         :
:.........................: putrid forms of man                :
:   Jakob Østergaard      : See him rise and claim the earth,  :
:        OZ9ABN           : his downfall is at hand.           :
:.........................:............{Konkhra}...............: