[Beowulf] Raid disk read performance issue in Linux 2.6, anyone seen this?
bogdan.costescu at iwr.uni-heidelberg.de
Wed Dec 8 11:10:40 EST 2004
On Tue, 7 Dec 2004, Craig Tierney wrote:
> I meant White Box distribution which is a rebuild of Red Hat Enterprise
> 3. It was an early release for Opteron and Itanium. Since then,
> the Gelato Foundation has taken over the rebuilds and should be
I don't think that this is "official" WhiteBox Linux. Their web page
only mentions x86 and x86_86 architectures. They might even don't know
about it... ;-)
The guy that initially built WhiteBox x64_64 and ia64, Pasi Pirhonen,
is now their TaoLinux maintainer (along with s390(x)).
> It isn't exact, but every single 2.6 based system I have tried
> has shown this problem. Every 2.4 based system has not shown this
It is indeed strange...
> I primarily used lmdd to test the performance of the filesystem. All
> I care about is big streaming IO.
ext3 and xfs (at least) care about the underlying sector size or RAID
stripe size. Have you paid attention to this when you formatted the
device (if you formatted after moving to the new computers) ? Do you
use something else between the physical device and the file-system,
like lvm (lvm1 in 2.4, lvm2 in 2.6) or software RAID ?
> I did try sgpdd which accesses the device directly and I saw the
> same behavior.
I never heard of this tool. A simple search also didn't found
anything. Care to provide a link ?
Could you run hdparm/zcav/dd/etc. reading directly from real SCSI
device (no lv*, md*) ? Yes, I know, some of these tools are not very
precise, but we're talking about almost an order of magnitude...
IWR - Interdisziplinaeres Zentrum fuer Wissenschaftliches Rechnen
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E-mail: Bogdan.Costescu at IWR.Uni-Heidelberg.De
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