[Stgt-devel] Performance of SCST versus STGT

[FUJITA Tomonori]

On Thu, 17 Jan 2008 12:48:28 +0300
Vladislav Bolkhovitin <vst at vlnb.net> wrote:

> FUJITA Tomonori wrote:
> > On Thu, 17 Jan 2008 10:27:08 +0100
> > "Bart Van Assche" <bart.vanassche at gmail.com> 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 at lists.berlios.de/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.