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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: iSCSI: Async events - SCSI and iSCSI
OK Mark - How about:
1.1 Asynchronous Message
An Asynchronous Message may be sent from the target to the initiator
without corresponding to a particular command. The target specifies the
status and reason for the event and sense data.
Byte / 0 | 1 | 2 | 3 |
/ | | | |
|7 6 5 4 3 2 1 0|7 6 5 4 3 2 1 0|7 6 5 4 3 2 1 0|7 6 5 4 3 2 1 0|
+---------------+---------------+---------------+---------------+
0|1|1| 0x32 |1| Reserved |
+---------------+---------------+---------------+---------------+
4| Reserved | DataSegmentLength |
+---------------+---------------+---------------+---------------+
8| LUN |
+ +
12| |
+---------------+---------------+---------------+---------------+
16/ Reserved /
+/ /
+---------------+---------------+---------------+---------------+
24| StatSN |
+---------------+---------------+---------------+---------------+
28| ExpCmdSN |
+---------------+---------------+---------------+---------------+
32| MaxCmdSN |
+---------------+---------------+---------------+---------------+
36| AsyncEvent | Reserved | Parameter1 or Reserved |
+---------------+---------------+---------------+---------------+
40| Parameter2 or Reserved | Parameter3 or Reserved |
+---------------+---------------+---------------+---------------+
44| Reserved |
+---------------+---------------+---------------+---------------+
48| Digests if any... |
+---------------+---------------+---------------+---------------+
/ DataSegment - Sense Data or iSCSI Event Data /
+/ /
+---------------+---------------+---------------+---------------+
Some Asynchronous Messages are strictly related to iSCSI while others
are related to SCSI [SAM2].
Please note that StatSN counts this PDU as an acknowledgeable event,
allowing initiator and target state synchronization.
1.1.1 AsyncEvent
The codes used for iSCSI Asynchronous Messages (Events) are:
0 A SCSI Asynchronous Event is reported in the sense data. Sense
Data that accompanies the report, in the data segment, identifies the
condition. Sending of a SCSI Event (Asynchronous Event Notification
in SCSI terminology) is controlled by a SCSI Control Mode Page bit.
1 Target requests Logout. This Async Message MUST be sent on the
same connection as the one being requested to be logged out.
Initiator MUST honor this request by issuing a Logout as early as
possible, but no later than Parameter3 seconds. Initiator MUST send
a Logout with a reason code of "Close the connection" to cleanly
shutdown the connection. If the initiator does not Logout in
Parameter3 seconds, the target should send an Async PDU with iSCSI
event code "Dropped the connection" if possible, or simply terminate
the transport connection. Parameter1 and Parameter2 are reserved.
2 Target indicates it will drop the connection.
The Parameter1 field indicates on what CID the connection will
dropped.
The Parameter2 field indicates, in seconds, the minimum time to wait
before attempting to reconnect.
Parameter3 indicates the maximum time to reconnect and/or restart
commands after the initial wait (Parameter2).
If the initiator does not attempt to reconnect and/or restart the
outstanding commands, within the time specified by Parameter3 or, if
Parameter3 is 0, the target will terminate all outstanding commands
on this connection, no other responses should be expected from the
target for the outstanding commands on this connection.
A value of 0 for Parameter2 indicates that reconnect can be attempted
immediately.
3 Target indicates it will drop all the connections of this
session.
The Parameter2 field indicates, in seconds, the minimum time to wait
before attempting to reconnect.
The Parameter3 field indicates the maximum time to reconnect and
restart commands after the initial wait (Parameter2).
If the initiator does not attempt to reconnect within the time
specified by Parameter 3 or, if Parameter 3 is 0, the session is
terminated. In this case, the target will terminate all outstanding
commands in this session; no other responses should be expected from
the target for the outstanding commands in this session. A value of
0 for Parameter2 indicates that reconnect can be attempted
immediately.
255 Vendor specific iSCSI Event - additional data MAY accompany the
report.
All other event codes are reserved.
1.1.2 Sense Data or iSCSI Event Data
For a SCSI Event this is the data that accompanies the report, in the
data segment, identifies the condition.
For an iSCSI Event additional data that MAY accompany the report
Mark Bakke <mbakke@cisco.com>@ece.cmu.edu on 07-09-2001 18:54:22
Please respond to Mark Bakke <mbakke@cisco.com>
Sent by: owner-ips@ece.cmu.edu
To: Julian Satran/Haifa/IBM@IBMIL
cc: ips@ece.cmu.edu
Subject: Re: iSCSI: Async events - SCSI and iSCSI
Julian-
I'd like to see them separate for two reasons:
- iSCSI and SCSI-level events are typically orthogonal, so they
probably won't usually end up being combined anyway. It would
be simpler for both the target and the initiator to not attempt
to combine them.
- Since the SCSI-level events use the data portion of the message
for sense data, that leave iSCSI events without any way to send
data of their own if there is a possibility of combining the
two. By keeping them separate, iSCSI could use the data portion
for text keys. In fact, Parameters 1, 2, and 3 might have been
easier to describe had they been communicated using text keys;
the processing of async messages is not a performance-critical
thing anyway.
That's about it. A target could send both in one message, but since
the desire to do this is probably an end case (a small percentage
of async messages might combine both), there's no reason why we
can't just have the target send two messages, and we end up with
a simpler, and for iSCSI events, more flexible, implementation for
both the initiator and target.
Anyway, I think that if we are going for a clear separation between
SCSI and iSCSI events, that it's even clearer if they are always
sent in separate messages.
Thanks,
Mark
Julian Satran wrote:
>
> Mark,
>
> As far as I recall it is not by chance. When we decided to go for a clear
> separation of SCSI and iSCSI events
> I saw no reason why a target will not want to send both, if it had them,
in
> one message.
> Is there something I am missing? Obviously this runs against your later
> request for text async messages.
>
> Julo
>
> Mark Bakke <mbakke@cisco.com>@ece.cmu.edu on 05-09-2001 23:09:12
>
> Please respond to Mark Bakke <mbakke@cisco.com>
>
> Sent by: owner-ips@ece.cmu.edu
>
> To: IPS <ips@ece.cmu.edu>
> cc:
> Subject: iSCSI: Async events - SCSI and iSCSI
>
> Julian-
>
> I was looking at Async Message some more, and noticed that there
> is nothing to stop a target from sending a message that includes
> both iSCSI and SCSI events, since each of these are communicated
> with a different set of fields. I would guess that this is not
> what is intended, and that the target ought to send one or the other.
>
> Can we add some text to say:
>
> A target may send this message as either a SCSI Event or an
> iSCSI Event, but not both. Either the SCSI Event or iSCSI
> Event field MUST be zero.
>
> --
> Mark A. Bakke
> Cisco Systems
> mbakke@cisco.com
> 763.398.1054
--
Mark A. Bakke
Cisco Systems
mbakke@cisco.com
763.398.1054
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