[Beowulf] mysterious slow SATA on one machine

David Mathog mathog at caltech.edu
Mon Mar 29 19:33:18 EDT 2010


> > David Mathog wrote:
> >Raw results from various experiments here:
> > 
> >   http://saf.bio.caltech.edu/pub/pickup/bonnie++.rtf
> >   http://saf.bio.caltech.edu/pub/pickup/sustained_write.rtf
> > 
> 
> Some progress, see updated files above.

And a step back...

With the latency set to 22 on the VGA, and 144 on the 
Sil 3114, three consecutive boots varying (and this is probably a red
herring) only the type of partition 5 (swap partition, which is the
first logical partition in the one extended partition, following the
first partition, which is both real and the boot partition)

Boot    Type    bonnie++ (-Per Chr- --Block-- -Rewrite- 
                   -Per Chr- --Block-- --Seeks-- line)
A       83      48104  91 65832  32 
                33587  13 48852  89 106061  16 219.9   1
B       82      47572  89 47176  18
                19601   6 35147  79 59726   8 188.2   1
C       83      48662  92 65424  26
                32901  12 48648  89 105560  15 214.9   1

Conversely, the sustained write test was about the same for all 3 boots,
although slightly (5%) faster for A,C than B.   Run the bonnie++ test
over and over during each uptime and the results come out more or less
the same.  Reboot, and they changed. Could the partition type really
matter?  Change it back, reboot, giving D:

D        82     48188  90 63984  27
                33609  13 47391  89 106234  16 217.9   1

So no, the partition type isn't the story, or at least not the whole
story. Something else must be going on. 

If feels like there is a bit somewhere that is blowing in the wind...

Regards,

David Mathog
mathog at caltech.edu
Manager, Sequence Analysis Facility, Biology Division, Caltech
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