[Beowulf] mysterious slow disk

[Bogdan Costescu]

On Thu, 6 Mar 2008, csamuel at vpac.org wrote:

> If the problem moves with the drive then you'll know it's that, and 
> if it stays then it's likely to be the MB or the cabling.

Sorry for the late jump...

IIRC, the OP had dual Athlon based nodes; there used to be some issues 
of slow I/O related to the usage of energy saving features of the CPUs 
and/or chipset. Have you already checked for such a situation ?

Another thing that comes to my mind: I have seen some SATA disks (I 
think from Hitachi) which have developed some bad sectors, which could 
be seen in the smartctl output. I have run the DFT on them and after 
choosing to rewrite the whole disk (I have forgotten the exact option 
name...) the disk was shown as good and there was no sign of bad 
sectors in the smartctl output. However, the access to disk was 
slower, especially the writes, for which the speed was aproximately 
halved. So, is it sure that the disk was never subjected to a 
manufacturer "diagnose and repair" tool ?

-- 
Bogdan Costescu

IWR, University of Heidelberg, INF 368, D-69120 Heidelberg, Germany
Phone: +49 6221 54 8869/8240, Fax: +49 6221 54 8868/8850
E-mail: bogdan.costescu at iwr.uni-heidelberg.de