RE: iscsi : default iscsi mode page settings.

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

I thought you where concerned about "boot duration"? julo


                                                                                         
                    "KRUEGER,MARJOR                                                      
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                    x1)"                  Subject:     RE: iscsi : default iscsi mode    
                    <marjorie_krueg        page settings.                                
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                    "KRUEGER,MARJOR                                                      
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I vote for making the exchange of some text parameters MANDATORY, with no
defaults.

Marj

> -----Original Message-----
> From: Robert Snively [mailto:rsnively@Brocade.COM]
> Sent: Thursday, September 20, 2001 10:48 AM
> To: 'Sanjeev Bhagat (TRIPACE/Zoetermeer)'; 'Santosh Rao'; IPS
> Reflector
> Subject: RE: iscsi : default iscsi mode page settings.
>
>
> It is true that default mode settings for Mode Pages
> are usually arranged between buyer and vendor for
> maximum convenience in the buyer's systems.  It is
> generally true that any setting of a Mode Page will
> allow the protocol to operate correctly, except a few,
> notably the first burst size parameter if
> ImmediateData is set to yes.
>
> On the other hand, some of the iSCSI text keyed
> parameters MUST be known before the protocol will
> operate correctly.  ImmediateData is certainly
> one of those.  As a result, you have two choices:
>
>    a)   Make the negotiation of all such parameters
>    MANDATORY during the login and after any
>    reset that may change them,  or;
>
>    b)   Define a default state that will be guaranteed
>    unless and until the parameter has been explicitly
>    changed.
>
> Your choice.
>
> Bob
>
> > -----Original Message-----
> > From: Sanjeev Bhagat (TRIPACE/Zoetermeer)
> [mailto:sbhagat@tripace.com]
> > Sent: Thursday, September 20, 2001 6:59 AM
> > To: 'Santosh Rao'; IPS Reflector
> > Subject: RE: iscsi : default iscsi mode page settings.
> >
> >
> > Santosh,
> >
> > Where did you find these SCSI Mode page settings? At least I
> > could not find
> > it in SAM-2 document? The mode select command is available in
> > SPI documents
> > but they are meant for particular SCSI device and not for
> > iSCSI device?
> >
> > Be it whatever the case I would like to ask why the default value of
> > MaximumBurstSize is 512 units and why is the default value of
> > FirstBurstSize
> > 128 units. remember each unit is 512 bytes as defined in iSCSI 7.9x
> > revisions so setting the default value of FirstBurstSize to
> > 128 units means
> > 65536 bytes or 64K Bytes and similarly the value of
> > Maximumburstsize is 256K
> > Bytes. Is it Ok to have the FirstBurstsize of 64KB??
> >
> > Sanjeev
> >
> > -----Original Message-----
> > From: Santosh Rao [mailto:santoshr@cup.hp.com]
> > Sent: Thursday, September 20, 2001 2:04 AM
> > To: IPS Reflector
> > Subject: iscsi : default iscsi mode page settings.
> >
> >
> > All,
> >
> > Speaking on the subject of default settings, some questions
> on recent
> > changes to the iscsi mode select pages......
> >
> > 1) Section 3 of rev 7.94 of the iscsi draft attempts to call
> > out default
> > values for the iscsi  mode pages. Per my understanding, there are no
> > defaults for SCSI mode pages, and all the setting are assumed to be
> > disabled, unless explicitly turned on/enabled through a mode select.
> >
> > IOW, the keys in scsi mode pages are defined to be enabling certain
> > features and the default settings are that these features are
> > turned off
> > unless a mode select is explicitly used to enable them.
> >
> > However, the iscsi mode pages seems to be using the opposite
> > policy and
> > is advertising default settings for mode pages, that too,
> > agreesive ones
> > at that! IOW, an initiator implemenation has to explicitly
> > issue a mode
> > select to disable/turn_off features rather than issue a
> mode select to
> > turn them on.
> >
> > Here's a few examples :
> >
> >    * default MaximumBurstSize : 512 units
> >    * default EMDP : 1 (i.e. modify data pointers is enabled
> by default
> > !)
> >    * default FirstBurstSize : 128 units. (i.e. initiators MUST use
> > solicited
> >      data, unless they explicitly turn it off using mode
> > select, since,
> > not
> >      sending solicited data when it has been negotiated
> > implies a target
> > may
> >      abort the I/O.
> >
> > I suggest that in keeping with the scsi mode pages, NO
> > default settings
> > be advertised for any iscsi mode
> > pages. i.e. all defaults are conservative (set to 0), unless
> > explicitly
> > turned on thru a mode select.
> >
> > Comments ?
> >
> > Regards,
> > Santosh
> >
> > "Mallikarjun C." wrote:
> >
> > > Matthew,
> > >
> > > I completely agree that the default should be "no"!  I
> pointed this
> > > out sometime ago myself.  Apart from what you point out,
> the default
> > > setting for "ImmediateData" seems to be at variance with the
> > > conservative default for "InitialR2T" ("yes").
> > >
> > > Julian, could you please consider this request?
> > >
> > > Regards.
> > > --
> > > Mallikarjun
> >
> > > "BURBRIDGE,MATTHEW (HP-UnitedKingdom,ex2)" wrote:
> > > >
> > > > Julian,
> > > >
> > > > Appendix D24 (ImmediateData) does not describe the result of
> > negotiation if
> > > > the two sides differ. I presume that since the default is "yes",
> > then only
> > > > if both sides agree to "no" is immediate data turned
> off.  Please
> > can this
> > > > be stated.
> > > >
> > > > Additionally, I feel that the default value for
> > ImmediateData should
> > be
> > > > "no".
> > > >
> > > > Similarly, there is no statement on MaxOutstandingR2T.
> Presumable
> > the
> > > > minimum is selected.
> >
> >
>