All but a few of the iSCSI parameters for are negotiated. They have
default values that are specified in the iSCSI spec. The initiator is
allowed to propose new values, which the target can accept or reject or
renegotiate. Technically speaking the target is also allowed to
propose new values that the initiator can accept or reject or
renegotiate, but COMSTAR always waits for the initiator to speak
first. For details, please refer to the spec itself (RFC 3720).
You can look in the COMSTAR source for details. Here are some pointers:
In iscsit_login_sm_init,
iscsit sets up the default values of all the parameters. The handling
of iscsi keys is spread over many routines downstream from
login_sm_process_request, login_sm_process_nvlist, and
iscsit_handle_key, but the base operational parameters are handled in iscsit_handle_operational_key.
Refer to that routine for details of the following:
Some of parameters for which COMSTAR will negotiate only the default
value include:
- We allow ImmediateData=yes, but not InitialR2T=yes. This means
that the only kind of "unsolicited first burst" we support is the
Immediate Data in the SCSI WRITE command PDU itself.
- We only allow MaxConnections=1, i.e. there is no support for
multiple connections per session (MC/S) at this time.
- We will negotiate only for DataPDUInOrder=yes
- We only negotiate for ErrorRecoveryLevel=0
- We only negotiate for MaxOutstandingR2T=1.
Modifying any of the above characteristics of COMSTAR would require an
RFE. As with any RFE in an open source project, you are free either
to lobby for us to undertake the work or to undertake the work yourself
and then contribute it back to the project. We would welcome
contributions. We would also welcome test partners who volunteer to
test one of these features if and when we have it under development!
Peter
Errol Neal wrote:
Jim wrote:
How do you modify those values?
Most parameters are modified (negotiated) from the point of view of
the iSCSI Initiator. For Solaris, this is detailed here: http://docs.sun.com/app/docs/doc/817-5093/fqnln?a=view
Which settings are not negotiated? I change the max number of outstanding RTTs to 16 (well below the limit :) ) and the settings were still negotiated at 1. Additionally, initial RTT is set to true - but on the initiator (SLES11), it's set to false/no
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