I'm playing around with performance tuning my disk access, but there is
something limiting my bandwidth to the disks. I was hoping you could
help me determine what.
My setup is a sil3132 controller, connected to a PMP with five disks
behind it. I'm using iostat to measure disk traffic and I'm using reads
via dd for testing.
When I'm accessing a single disk, the bandwidth is 70 - 80 MiB/s. When
I access a second disk, the bandwidth is about 50 MiB/s/disk, and all
five results in 25 MiB/s/disk. In other words, something is limiting
things to about 100 MiB/s. Now the question is what that limiting
factor is.
The PCIe bus can sustain 250 MiB/s, so even with overhead that should
be plenty. The SATA links are in theory 300 MiB/s, so that can't be it
either. The remaining factors are the controller and the multiplier
chip, and/or the way we access them.
Tejun, what kind of throughput have you seen when you have been testing
the sil3132 and multipliers?
Rgds
--
-- Pierre Ossman
Linux kernel, MMC maintainer http://www.kernel.org
rdesktop, core developer http://www.rdesktop.org
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