Re: iSCSI - error recovery .. more basic questions

["Mallikarjun C." <cbm@rose.hp.com>]

Chaavi,

Responses below.
--
Mallikarjun

Mallikarjun Chadalapaka
Networked Storage Architecture
Network Storage Solutions Organization
Hewlett-Packard MS 5668
Roseville CA 95747
cbm@rose.hp.com

> 1. In case of connection and session recovery, the draft says that it is implicity for the target to
abort/terminate all active tasks. During task reassignment scenario when will the target issue a response with
the "Task Still Allegiant" error message as it assumed that all active tasks have already been terminated?

Section 6.1.2 clearly specifies when this response is to be returned.  Also, look at
6.12.3, which is connection recovery, it doesn't say that the tasks are terminated - in
fact the "recovery" part of connection recovery is not to terminate the tasks.

> 2. Section 6.4 says
>
>
> "Explicit violations of the PDU layout rules stated in this document are format errors."
>
>
> How does the receiving party (initiator / target) detect these PDU layout errors? Is an error in format of
text parameters an example of format errors? What are the other kinds of format errors? some examples would
help

I would say that illegal values for fields (for ex., Cmd.ATTR = 6) are potentially layout errors.
I don't consider text parameter format errors (for ex., MaxConnections=hello) as format errors
to be treated under this rule - look for ways to deal with the latter in the archives/draft (there
were extensive discussions on this topic).

> 3. When will an initiator issue an ABORT_TASK_SET to the target? Will it based on any error responses /
messages received from the target? Will it happen during session or connection recovery? Similarly other
commands like CLEAR_TASK_SET, TARGET_WARM_RESET, etc.,

All these are SCSI operations, and SCSI layer would issue them when appropriate - to be
transported by iSCSI.

Target cold reset is the new function that iSCSI brings to table, and it ought to be deployed
when a power-on reset of the SCSI device is desired.  We had already talked about
allegiance reassignment earlier.

> 4. What is the basic difference between Connection recovery / reinstatement?

Connection recovery refers to recovering the tasks active on a connection when
a connection fails - all being transparent to SCSI.   Section 4.3.4 clearly spells
out how the reinstatement may be related to recovery.

> 5. What is the basic difference between Session recovery / reinstatement?

Session reinstatement is one case (that of active ISID on the target) of session
recovery - again, 4.3.5 clearly defines this case.....

> 6. On Session reinstatement should all the session parameters be negotiated again?

Anytime TSIH=0, it's the leading connection and all LO parameters must be
negotiated.