Interpretation of Logical unit Reset behavior
Elliott, Robert (Server Storage)
Elliott at hp.com
Fri Oct 18 16:08:22 PDT 2002
* From the T10 Reflector (t10 at t10.org), posted by:
* "Elliott, Robert (Server Storage)" <Elliott at hp.com>
This question was raised in March 2001 during the negotiation rewrite,
01-128r2 (1 May 2001) SPI-4 reset cleanup
added the rule that LOGICAL UNIT RESET shall not affect the negotiation.
Negotiated settings are a property of the target port shared by all the
logical units. In a target with multiple logical units, reset of one of
the logical units shouldn't affect the others' ability to communicate.
SAM-2 just says the logical unit should be returned to a power-on-like
state, not the target port. TARGET RESET does the target port
Rob Elliott, elliott at hp.com
Industry Standard Server Storage Advanced Technology
> -----Original Message-----
> From: gerry.houlder at seagate.com [mailto:gerry.houlder at seagate.com]
> Sent: Friday, October 18, 2002 4:26 PM
> To: t10 at t10.org
> Subject: Interpretation of Logical unit Reset behavior
> * From the T10 Reflector (t10 at t10.org), posted by:
> * gerry.houlder at seagate.com
> A contradiction has been pointed out for the description of
> the Logical Unit Reset behavior. In particular, note the
> requirements I have marked with double brackets << >>.
> From SPI - 4 or 5:
> 16.5.6 LOGICAL UNIT RESET
> The LOGICAL UNIT RESET message is defined in the SCSI Architecture
> Model-2 standard.
> Receipt of the LOGICAL UNIT RESET message after an I_T_L
> nexus has been
> established is a logical
> unit reset event as defined in the SCSI Architecture
> Model-2 standard.
> In addition to the requirements in the SCSI Architecture Model-2
> standard the SCSI target port shall go to
> the BUS FREE phase following the successful receipt of the
> LOGICAL UNIT
> RESET message.
> <<A logical unit reset has no effect on the transfer agreement.>>
> From SCSI Architecture Model-2 standard
> 5.9.7 Logical unit reset
> A logical unit reset is:
> a) The action in response to a LOGICAL UNIT RESET task management
> request (see 6.6) or some other
> logical unit reset event; or
> b) One of the actions in response to a TARGET RESET task management
> function (see 6.7) or a hard reset
> (see 5.9.6).
> The definition of logical unit reset events is dependent
> on the SCSI
> transport protocol.
> To process a logical unit reset the logical unit shall:
> a) Abort all tasks as described in 5.7;
> b) Clear a CA (see 18.104.22.168) or ACA (see 22.214.171.124)
> condition, if one is
> c) Release all reservations established using the reserve/release
> management method (persistent reserva-tions
> shall not be affected);
> <<d) Return the logical unit's operating mode to the
> appropriate initial
> conditions, similar to those conditions that
> would be found following device power-on.>> The MODE
> SELECT parameters
> (see SPC-2) shall be restored
> to their last saved values if saved values have been
> established. MODE
> SELECT parameters for which no
> saved values have been established shall be returned to
> their default
> e) Set an unit attention condition (see 5.9.5); and
> f) Initiate a logical unit reset for all dependent logical
> units (see
> In addition to the above, the logical unit shall perform
> any additional
> functions required by the applicable standards.
> The wording from SPI says "no effect on transfer agreement",
> meaning the target has to remember the transfer agreement
> even though everything else is being reset. The SAM wording
> says "similar to power on", which certainly includes
> resetting the transfer agreement. These conditions certainly
> conflict with each other. How do we resolve the conflicting wording?
> The single LUN targets I am familiar with reset all the same
> things (including the transfer agreement) for both of these
> functions. Are these devices in violation of the standard?
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