[Stgt-devel] Performance of SCST versus STGT

FUJITA Tomonori fujita.tomonori
Thu Jan 17 10:40:52 CET 2008

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.

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