On Sep 15, 2009, at 4:28 PM, Greg Freemyer wrote:
I've actually been doing some of those benchmarks here. Given a Silicon Image 3124 card in a x1 PCI-e slot, my maximum throughput should be about 250MB/s (PCI-e limitation). My drives behind the pm are all capable of about 80MB/s, and I have 4 drives. What I've found is that when accessing one drive by itself, I get 80MB/s. When accessing more than one drive, I get a total of about 120MB/s, but it's divided by however many drives I'm accessing. So, two drives is roughly 60MB/s each, 3 drives about 40MB/seach, and 4 drives about 30MB/s each.Doug, I hate to ask the obvious, but you do have a 3Gbit/sec connection between the controller and the PM, right?
According to the kernel dmesg output, yes, I have a 3GBit/s connection. However, I had the very same niggling doubts as you, and I don't have a SATA bus analyzer to prove it to myself.
I only ask because your 120MB/sec is about right for a 1.5Gbit/sec connection. I was under the impression you should max out closer to 250MB / sec with a good controller and PM and a 3.Gbit/sec connection. I have not done any testing myself.
I agree with this sentiment 100%. I don't have a good answer for why it topped out where it did, and that's one of the things I'm still trying to get an answer to.
-- Doug Ledford <dledford@xxxxxxxxxx> GPG KeyID: CFBFF194 http://people.redhat.com/dledford InfiniBand Specific RPMS http://people.redhat.com/dledford/Infiniband
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