[ILUG] Linux SMP on Xeons

[Wesley Darlington]

Hi,

On Thu, Jun 15, 2000 at 05:31:48PM +0100, David Murphy wrote:
> Quoting <20000615170057.A3124 at tux.blackstar.co.uk>
> by Wesley Darlington <wesley at blackstar.co.uk>:
> 
> > Hi,
> > 
> > On Thu, Jun 15, 2000 at 01:05:43PM +0100, Paul Jakma wrote:
> > > On Thu, 15 Jun 2000, Paul Trainor wrote:
> > > > AMI Megaraid should do the job.
> > > what sort of performance do they give? from what i've seen on linux-raid
> > > they're dreadfully dreadfully slow, esp. at RAID5.
> > 
> > I recommend the AMI megaraid 1500 elite. They *rock*. 128MB battery backed
> > cache.
> 
> Does it let you do RAID 1+0 or 0+1? Gateway delivered an ALR 7200 in
> here this morning, and it came with an AMI RAID card, and we couldn't
> for the life of us figure out how to mirror a stripe. Of course, we
> were still in shock from the sight of large styrofoam mouldings
> holding fans set at right angles to each other, so perhaps we missed
> it...

Yes, one can do (only one of) 1+0 or 0+1. I've forgotten how to do it,
though. Something like making a 0 (or was it 1) and then marking it as
"can be extended" inside the megamgr/bios thing.

I might have notes in work on this. Email me and I'll see if I can find
them tomorrow morning. It is kinda described in the downloadable ami
manual, but it's fairly well hidden and hard to follow. At least, that
was what I found.

If it's a 1500 or better that you have, benchmark both this and raid5
for your app. If it's something crap like a 466, throw it out ;-) and
get something decent. :-)  I've heard reports that even the 1400 is
a naff card.

Also, when using raid cards under linux, I've found it useful to apply
andrea arcangeli's elevator starvation patch. It makes the difference
between the machine being usable under heavy sustained IO and being
totally unusable. :-)

All the best,
Wesley.