Re: iscsi : default iscsi mode page settings.

[Santosh Rao <santoshr@cup.hp.com>]

"Sanjeev Bhagat (TRIPACE/Zoetermeer)" wrote:

> I would still go in favour of running a mode sense rather than using a login
> key because
> 1. by providing a value in login key essentially means that we are doing
> some sort of mode select to the target

Sanjeev,

I dis-agree with the above. A login key serves as a mechanism to either
negotiate or query for a parameter value.By sending :
FirstBurstSize=?

you could query the target for its current setting of this parameter and you
would achieve this in a more optimal manner than having to send one extra SCSI
command on the wire during session establishment solely for the purpose of
querying this key.

In addition, even if the initiator attempted to negotiate this key, the target
is allowed to send back a different value for this key based on the buffering
abilities of the target.

For ex :
I -> T : MaximumBurstSize=128
T -> I : MaximumBurstSize=8

is a valid negotiation and the target is allowed to send back a default setting
for all initiators without allowing any initiators to make a change.

Thus, the login keys are as effective, but more optimal in use and more
accurate in scope, than the use of scsi mode sense/select for querying/setting
the FirstBurstSize.



> 2. if multiple initiators send different values of firstburstsize then
> target has to behave accordingly with all different targets.

See above.

Regards,
Santosh

>
> This goes completely against the semantics of mode sense and mode select
> defined in SCSI specifications. Any such parameteres are although
> settable/changeable by clients but are mainly the properties of SCSI
> LUs/targets.
>
> Mode sense command from initiator will simplify the logic at target's end as
> well.
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