[ofa-general] OFED SRP Client / StorageGear Target / Performance with Modified Write Protocol

[Roland Dreier]

 > We have been doing a fair amount of performance testing on our SRP target.
 > One thing we found early on was that client writes were considerably slower
 > than client reads. We addressed this by patching the SRP client code so
 > that it could include the client write data in the SRP CMD IU if it would
 > fit. This notion is in iSER but is not in standard SRP. Architecturally,
 > the capability is signaled using an additional data buffer format bit.
 > We find that client write performance is considerably improved by using
 > this capability. We are calling SRP spec compliant writes "standard
 > writes" and our modified writes "iu data writes".

I think this may make sense but you probably want to involve T10 to
get it standardized somehow.  Also, although I know having a big IOP
number is important for various non-technical reasons, are there any
realistic storage workloads that do lots of single-block writes?

Also I guess you need to use giant IUs to be able to hold at least one
block in the IU?

 - R.