[Beowulf] Raid disk read performance issue in Linux 2.6, anyone seen this?

[Bogdan Costescu]

On Mon, 6 Dec 2004, Craig Tierney wrote:

> an a Opteron dual 1.8 Ghz and an Itanium dual 1.4 Ghz, both running
> White Box.

I seriously doubt this. WhiteBox for Itanium ? Since when ? :-)

> The same physical computer was not used in all tests, or even for
> the same architecture.

That's messy. Different devices can behave differently with the same 
driver on different architectures, due to differences in PCI 
implementation, cache alignment, etc. I don't say however that this 
explains the big difference that you saw between 2.4 and 2.6...

> However, since the behavior seems to cross different architectures
> with different interfaces, I don't think the problem is with an
> individual server.

Based on the description so far, I would lean towards file-system
differences. But you did not specify how you got the speed figures:  
hdparm, bonnie, zcav, iozone, tiobench, something else ? The main
question being: at device level or file-system level ?

-- 
Bogdan Costescu

IWR - Interdisziplinaeres Zentrum fuer Wissenschaftliches Rechnen
Universitaet Heidelberg, INF 368, D-69120 Heidelberg, GERMANY
Telephone: +49 6221 54 8869, Telefax: +49 6221 54 8868
E-mail: Bogdan.Costescu at IWR.Uni-Heidelberg.De