Chris Worley, on 08/25/2010 12:31 AM wrote:
I also have an impression that Linux I/O subsystem has some performance
problems. For instance, in one recent SCST performance test only 8 Linux
initiators with fio as a load generator were able to saturate a single SCST
target with dual IB cards (SRP) on 4K AIO direct accesses over an SSD
backend. This rawly means that any initiator took several times (8?) more
processing time than the target.
While I can't tell you where the bottlenecks are, I can share some
performance numbers...
4 initiators can get>600K random 4KB IOPS off a single target...
Hmm, on the data you sent me only 8 initiators were capable to do so...
I'm glad to see an improvement here ;).
which is ~150% of what the Emulex/Intel/Microsoft results show using 8
targets at 4KB (their 1M IOPS was at 512 byte blocks, which is not a
realistic test point
From my, a storage developer's, POV it isn't about if this test is
realistic or not. 512 bytes tests are good if you want to test how
processing effective your I/O stack, because they produce the max
possible CPU/memory/hardware interaction load. Since processing power
isn't unlimited, in case if it is a bottleneck, N IOPS on 512b < N IOPS
on 4K * 8 and system with more effective processing will have better
numbers.
Vlad
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