Bad performance with aacraid

Hi there, 

I know there's been a lot of discussion about this issue but not really
a disclosing answer until now or I must have missed a post, but this is
as far as i got:

I am having the same problem like others, performance in raid5 is very
poor, single drive performance is better. I get the same 40-55 MB/s with
3 seagate 10k disks in raid 5 like others have posted before and 68 MB/s
with just a single disk. I don't have a dell, so forgive me for posting
here, but here seems where the discussion is at. I have an intel based
system (intel board 7501BR2, intel chassis) with add-on adaptec 2120s
and one intel xeon 2ghz. Some pecular things:
(everything is measured in hdparm, I checked with bonnie if it was
hdparm but no bonnie wasn't any better)
single cpu kernels seem to give slightly better performance (more stable
figures and 2 mb/s higher in the highest cases, but still around 55
MB/s). Even so kernels during installation of distributions give even
better performance (especially the one from gentoo in my case which gave
me 60 mb/s, but as I install a new kernel or the kernel that comes with
the distro performance is back at the 45-50 MB/s)

Suse 8.2 live cd gives me the performance i was expecting, around 100
MB/s with 3 disk raid5 and 2 disks in raid0 even goes upto 120 MB/s. But
I don't like Suse and I don't know what Suse will do when I really
install it.
The adaptec configuration cd (which I think runs on redhat, but it
doesn't give you much info on kernelspecs, although the /dev/aac gives
clues to bsd but i am not sure as i already said) gives me almost
simular speeds for single disks and raid in hdparm, all 68 MB/s and no
variances raid5 around 1 MB/s higher but this varies a bit.

So now I have been looking into the Suse kernel but I can not find
anything special why the performance is so good. Could it be that you
use the cdrom as your main filesystem? Are these figures produced with
the suse livecd absurd? Has anyone found a way to get the performance
out of adaptec scsi controllers when it didn't work out in the first
place?

Thanks in advance

Regards,
Bas

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