[Beowulf] Slow RAID reads, no errors logged, why?

[Jörg Saßmannshausen]

Hi David,

I am wondering if that is not what you would expect. 
The long SMART test is quite thorough so the disc will be subject to quite a 
bit of stress. Thus, it could well be that the controller is slowing down the 
rest of the RAID as there is a bottle neck. So from that angle it does make 
sense to me. 
This is, however, just speculation from my side.

All the best from a chilly London

Jörg


Am Montag, 19. März 2018, 16:50:51 GMT schrieb David Mathog:
> Found the problem.  Well, sort of.
> 
> The issue is that when a long SMART test runs on any disk on the system
> (A) which has this problem the IO goes down to 30Mb/s.  It doesn't
> matter which disk is running the test.  The system we have which is most
> like it (C) does not have this issue.
> 
>             A       C
> Centos     6.7     6.9
> RAM        512     512 Gb
> CPUs       56      40  (actually threads)
> PowerEdge  T630    T630
> Xeon       E5-2695 E5-2650 (both v3)
> speed      2.30GHz 2.30Ghz
> cpufreq?   yes     no
> PERC       H730    H730P
> SAS disk   ST2000NM0023
> SAS disk           ST4000NM0005
> 
> There are a bunch of small differences between the two systems so it is
> hard to say for sure which is the actual culprit.
> 
> I will put this out on the smartmontools list and see if anybody has
> seen it before.
> 
> Regards,
> 
> David Mathog
> mathog at caltech.edu
> Manager, Sequence Analysis Facility, Biology Division, Caltech
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