Re: iSCSI read/write cost difference

["Julian Satran" <Julian_Satran@il.ibm.com>]

Did the input data aggregate the final
status with data or send it separately.
If the response was sent separately
that may explain why short writes perform better as three interrupts are
involved in a short read as opposed to 2 interrupts for writes (I assume
you use immediate data).

Julo

mingz <mingz@ele.uri.edu>
Sent by: owner-ips@ece.cmu.edu

17/04/03 20:03

Please respond to
mingz@ele.uri.edu

To	"Anshul Chadda" <anshul.chadda@trebia.com>
cc	ips@ece.cmu.edu
Subject	Re: iSCSI read/write cost difference

InitialR2T=No , ImmediateData=Yes , and i am not sure
about the answer for 
last question.

under is all the values.
-----------------------------------------
../common/iscsi_manage init restore host=$1
../common/iscsi_manage init force v=1800 host=$1
../common/iscsi_manage init set 
TargetName=iqn.2002-10.edu.unh.iol.iscsi.draft18-target_$2 host=$1
../common/iscsi_manage init set 
InitiatorName=iqn.1999-11.edu.unh.iol.iscsi.draft18-initiator host=$1
../common/iscsi_manage init set InitiatorAlias=UNH-Draft18-Initiator host=$1
../common/iscsi_manage init set MaxConnections=4 host=$1
../common/iscsi_manage init set HeaderDigest=CRC32C,None host=$1
../common/iscsi_manage init set DataDigest=CRC32C,None host=$1
../common/iscsi_manage init set InitialR2T=No host=$1
../common/iscsi_manage init set ImmediateData=Yes host=$1
../common/iscsi_manage init set MaxRecvDataSegmentLength=12288 host=$1
../common/iscsi_manage init set FirstBurstLength=16384 host=$1
../common/iscsi_manage init set MaxBurstLength=32768 host=$1
../common/iscsi_manage init set OFMarker=No host=$1
../common/iscsi_manage init set IFMarker=Yes host=$1
../common/iscsi_manage init set IFMarkInt=4096~32768 host=$1
../common/iscsi_manage init set OFMarkInt=1024~8192 host=$1
../common/iscsi_manage init set DefaultTime2Wait=10 host=$1
../common/iscsi_manage init set DefaultTime2Retain=6 host=$1
../common/iscsi_manage init set MaxOutstandingR2T=4 host=$1
../common/iscsi_manage init set DataPDUInOrder=No host=$1
../common/iscsi_manage init set DataSequenceInOrder=No host=$1
../common/iscsi_manage init set ErrorRecoveryLevel=0 host=$1
../common/iscsi_manage init snack d=y host=$1
../common/iscsi_manage init snack s=y host=$1
../common/iscsi_manage init force i=2 host=$1
../common/iscsi_manage init force p=2 host=$1


On Thursday 17 April 2003 12:39, you wrote:
> What are the negotiated values of InitialR2T and ImmediateData in
your
> setup? Also, does the target piggyback SCSI Response in the Final
Datain
> pdu?
>
>
> -----Original Message-----
> From: owner-ips@ece.cmu.edu [mailto:owner-ips@ece.cmu.edu]On Behalf
Of
> mingz
> Sent: Thursday, April 17, 2003 12:10 PM
> To: ips@ece.cmu.edu
> Subject: iSCSI read/write cost difference
>
>
> I recently did some experiments on iSCSI benchmarking. I used the
UNH iSCSi
> ref18_03 implementation and use a ram based scsi device for iscsi
target
> use.
> so there is no any disk overhead.
>
> I used a linux kernel module to send fixed size read/write requests
to
> iscsi initiator, which eventually will be filled by iscsi target.
i use
> interl pro1000 gigabit nic and intel 470 gigabit switch. and both
initiator
> and target use same type piii 866 pc with 1g ram.
>
> now the IOPS result shows that
>
>                  
               
2k                
                 4k
               
                 8k
               
                 16k
               
                 32k
> read                
                 1975
               
1781                
1557                
1081                
767
> write                
 2877              
  2225              
  1588              
  812              
               
   533
>
> for small reuqests, read is slower than write, while for large requests,
> read
> is faster than write. i redo the experiments on another enviroment,
also
> get similar results.
>
> can anybody explain why this happens?
>
> thanks a lot.
>
>
> ming

-- 
 --------------------------------------------------
| Ming Zhang, PhD. Student              
                     
| Dept. of Electrical & Computer Engineering       
| College of Engineering              
            
| University of Rhode Island            
          
| Kingston RI. 02881                
                 
| e-mail: mingz@ele.uri.edu              
         
| Tel. (401) 874-2293 Fax  (401) 782-6422        
 
| http://www.ele.uri.edu/~mingz            
        
 --------------------------------------------------