Christopher McCrory wrote:
Hello...
I searched though the mailing list archives and didn't see any mention
of this. I have a rhel 5.1 x86_64 server connected to a NetApp via two
qlogic HBAs (1). I can get 300-350MBytes/sec using a single controller.
However when I configure multipath (3) and use two FC connections ( one
from each FC card), I do not see twice the performance (3), but the same
performance as with a single card. I believe I have multibus enabled
(4).
Should I see twice the performance? Or are two FC cards only good for
failover?
You're not even saturating one 4Gb link. Adding a second isn't going to do much
for sustained throughput, since the disks themselves are the bottleneck, but it
will help for burst throughput thanks to caching on the array controller. This
makes a substantial difference for plenty of real-world workloads, which may or
may not include yours, though it's more difficult to measure with a synthetic
benchmark.
The real performance benefit comes when you're using extremely high-end arrays,
or using multiple arrays on the fabric simultaneously.
-- Chris
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