Re: Performance of SCST versus STGT

[Vladislav Bolkhovitin <vst-d+Crzxg7Rs0@public.gmane.org>]

Bart Van Assche wrote:
> On Jan 22, 2008 12:33 PM, Vladislav Bolkhovitin <vst-d+Crzxg7Rs0@public.gmane.org 
> <mailto:vst-d+Crzxg7Rs0@public.gmane.org>> wrote:
>>
>>  What are the new SRPT/iSER numbers?
> 
> You can find the new performance numbers below. These are all numbers 
> for reading from the remote buffer cache, no actual disk reads were 
> performed. The read tests have been performed with dd, both for a block 
> size of 512 bytes and of 1 MB. The tests with small block size learn 
> more about latency, while the tests with large block size learn more 
> about the maximal possible throughput.

If you want to compare performance of 512b vs 1MB blocks, your 
experiment isn't fully correct. You should use "iflag=direct" dd option 
for that.

> ............................................................................................. 
> 
> .                           .   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       .
> .............................................................................................
> 
> My conclusion from the above numbers: the performance difference between 
> STGT and SCST is small for a Gigabit Ethernet network. The faster the 
> network technology, the larger the difference between SCST and STGT.

This is what I expected

> Bart.