SUMMARY (partial): UFS slowness on Opteron

From: joe fletcher <>
Date: Wed Oct 15 2008 - 10:21:05 EDT
It's memory management on the Opterons. If we rip out most of the DIMMs it
speeds up. The machine originally had 256Gb and was pushing data half the
speed of our other machines with 128Gb fitted. If we run the tests with 32Gb
it behaves fine. We're playing with the hardware config to find out where the
tiping point is.





This is a bit woolly so apologies in advance.

Got some new x4600, 8x quad core Opteron boxes, 256Gb RAM attached to EMC
Clariion cx380s via Emulex LP10K HBAs. Kernel rev is 127112-11. We have a big
financial app that we're trying to migrate from a 6900 but when it comes to
filesystem performance it's dragging.

We've done some testing with iozone and the Opterons seem to be consistently
slower than the SPARCs. For example on one of our write tests the AMDs do it
in approx 1 min whereas an old v490 can do the same test in under 20s.

We discovered last night that if we use ZFS we can get the AMDs to behave
however we're not sure about ZFS support for the application.

We've tried various tuning eg maxphys, sd-max-transfer, sd throttling and so
on. Things that seem to work on the SPARCs provide no apparent benefit on the
AMDs even though the docs indicate they should.

Does anyone know of where we might look to get UFS to perform up to


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Received on Wed Oct 15 10:28:01 2008

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