Re: Performance of SCST versus STGT

[Vladislav Bolkhovitin <vst@vlnb.net>]

FUJITA Tomonori wrote:
> On Thu, 17 Jan 2008 10:27:08 +0100
> "Bart Van Assche" <bart.vanassche@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@lists.berlios.de/msg00004.html

Please don't confuse multithreaded latency insensitive workload with 
single threaded, hence latency sensitive one.

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