[Stgt-devel] Performance of SCST versus STGT

[Vladislav Bolkhovitin]

Bart Van Assche wrote:
> On Jan 24, 2008 8:06 AM, Robin Humble <robin.humble+stgt at anu.edu.au> wrote:
> 
>>On Tue, Jan 22, 2008 at 01:32:08PM +0100, Bart Van Assche wrote:
>>
>>>.............................................................................................
>>>.                           .   STGT read     SCST read    .    STGT read      SCST read    .
>>>.                           .  performance   performance   .   performance    performance   .
>>>.                           .  (0.5K, MB/s)  (0.5K, MB/s)  .   (1 MB >MB/s)   (1 MB, MB/s)  .
>>>.............................................................................................
>>>. Ethernet (1 Gb/s network) .      77             78       .         77            89       .
>>>. IPoIB    (8 Gb/s network) .     163            185       .        201           239       .
>>>. iSER     (8 Gb/s network) .     250            N/A       .        360           N/A       .
>>>. SRP      (8 Gb/s network) .     N/A            421       .        N/A           683       .
>>>............................................................................................
>>
> 
> Results with /dev/ram0 configured as backing store on the target (buffered I/O):
>                     Read          Write             Read          Write
>                   performance   performance       performance   performance
>                   (0.5K, MB/s)  (0.5K, MB/s)      (1 MB, MB/s)  (1 MB, MB/s)
> STGT + iSER           250          48                 349          781
> SCST + SRP            411          66                 659          746

Ib_rdma_bw now reports 933 MB/s on the same system, correct? Those 
~250MB/s difference is what you will gain with zero-copy IO implemented 
and what STGT with the current architecture has no chance to achieve.

> Results with /dev/ram0 configured as backing store on the target (direct I/O):
>                     Read          Write             Read          Write
>                   performance   performance       performance   performance
>                   (0.5K, MB/s)  (0.5K, MB/s)      (1 MB, MB/s)  (1 MB, MB/s)
> STGT + iSER             7.9         9.8               589          647
> SCST + SRP             12.3         9.7               811          794
> 
> Bart.
>