Erez Zilber wrote:
FUJITA Tomonori wrote:
On Thu, 17 Jan 2008 12:48:28 +0300
Vladislav Bolkhovitin <vst@xxxxxxxx> wrote:
FUJITA Tomonori wrote:
On Thu, 17 Jan 2008 10:27:08 +0100
"Bart Van Assche" <bart.vanassche@xxxxxxxxx> wrote:
Hello,
I have performed a test to compare the performance of SCST and STGT.
Apparently the SCST target implementation performed far better than
the STGT target implementation. This makes me wonder whether this is
due to the design of SCST or whether STGT's performance can be
improved to the level of SCST ?
Test performed: read 2 GB of data in blocks of 1 MB from a target (hot
cache -- no disk reads were performed, all reads were from the cache).
Test command: time dd if=/dev/sde of=/dev/null bs=1M count=2000
STGT read SCST read
performance (MB/s) performance (MB/s)
Ethernet (1 Gb/s network) 77 89
IPoIB (8 Gb/s network) 82 229
SRP (8 Gb/s network) N/A 600
iSER (8 Gb/s network) 80 N/A
These results show that SCST uses the InfiniBand network very well
(effectivity of about 88% via SRP), but that the current STGT version
is unable to transfer data faster than 82 MB/s. Does this mean that
there is a severe bottleneck present in the current STGT
implementation ?
I don't know about the details but Pete said that he can achieve more
than 900MB/s read performance with tgt iSER target using ramdisk.
http://www.mail-archive.com/stgt-devel@xxxxxxxxxxxxxxxx/msg00004.html
Please don't confuse multithreaded latency insensitive workload with
single threaded, hence latency sensitive one.
Seems that he can get good performance with single threaded workload:
http://www.osc.edu/~pw/papers/wyckoff-iser-snapi07-talk.pdf
But I don't know about the details so let's wait for Pete to comment
on this.
Perhaps Voltaire people could comment on the tgt iSER performances.
We didn't run any real performance test with tgt, so I don't have
numbers yet. I know that Pete got ~900 MB/sec by hacking sgp_dd, so all
data was read/written to the same block (so it was all done in the
cache). Pete - am I right?
As already mentioned, he got that with IB SDR cards that are 10 Gb/sec
cards in theory (actual speed is ~900 MB/sec). With DDR cards (20
Gb/sec), you can get even more. I plan to test that in the near future.
Are you writing about a maximum possible speed which he got, including
multithreded tests with many outstanding commands or about speed he got
on single threaded reads with one outstanding command? This thread is
about the second one.
Erez
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