[Stgt-devel] Performance of SCST versus STGT

Bart Van Assche bart.vanassche
Fri Jan 18 11:30:47 CET 2008

On Jan 17, 2008 6:45 PM, Pete Wyckoff <pw at osc.edu> wrote:
> There's nothing particularly stunning here.  Suspect Bart has
> configuration issues if not even IPoIB will do > 100 MB/s.

Regarding configuration issues: the systems I ran the test on probably
communicate via PCI-e x4 with the InfiniBand HCA's. With other systems
with identical software and with PCI-e x8 HCA's on the same InfiniBand
network I reach a throughput of 934 MB/s instead of 675 MB/s (PCI-e
x4). This is something I only found out today, otherwise I would have
run all tests on the systems with PCI-e x8 HCA's.

So the relative utilization of the InfiniBand network is as follows:
* STGT + iSER, PCI-e x4 HCA: 324/675 = 48% (measured myself)
* STGT + iSER, PCI-e x8 HCA: 550/934 = 59%
* SCST + SRP, PCI-e x4 HCA: 600/675 = 89% (measured myself)

Or: SCST uses the InfiniBand network much more effectively than STGT.


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