REC ELS parameter field

Kevin D Butt kdbutt at us.ibm.com
Mon Mar 23 12:37:15 PDT 2009


Formatted message: <a href="http://www.t10.org/cgi-bin/ac.pl?t=r&f=r0903232_f.htm">HTML-formatted message</a>

Kevin,
Sorry, we did confuse two fields.
The parameter field of the header is always set to zero.
The data transfer count field (used for FCP_RO) is set with bytes 
read/written unless an error occurs internal to the tape drive which 
requires the entire command to be redriven.  In that case, the data 
transfer count field of the LS_ACC is set to zero to indicate an FCP_RO of 
zero.  The intent is for the initiator port to discard any previously 
received data and redrive the command by sending an SRR with a relative 
offset of zero.
Kevin D. Butt
SCSI & Fibre Channel Architect, Tape Firmware
MS 6TYA, 9000 S. Rita Rd., Tucson, AZ 85744
Tel: 520-799-5280
Fax: 520-799-2723 (T/L:321)
Email address: kdbutt at us.ibm.com
http://www-03.ibm.com/servers/storage/ 
From:
"Kevin Jones" <kevin.jones at hp.com>
To:
Kevin D Butt/Tucson/IBM at IBMUS, "Kevin Jones" <kev at bri.hp.com>
Cc:
bob.nixon at emulex.com, t10 at t10.org, Dale.Lafollette at sun.com
Date:
03/19/2009 12:30 AM
Subject:
Re: REC ELS parameter field
Kevin,
I am still somewhat confused.
The frame header parameter field of a REC ELS request is usually
set to the task retry identifier (assuming TRID is enabled).
You stated:
> The parameter field of LS_ACC is the same as theparameter field of REC 
unless
which suggests you set the REC response frame header parameter
field to TRID ?
> unless an error occurs internal to the tape drive which requires
> the entire command to be redriven. In that case, the parameter
> field of the LS_ACC is set to zero
which suggests that in the event of an error, the parameter field
switches from being a TRID to being a "data transferred" indicator,
which would be a duplication of REC.LS_ACC.Word10 (FC4VALUE) ?
Regards
Kevin Jones
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On Tue, 17 Mar 2009 16:11:00 -0000, Kevin D Butt <kdbutt at us.ibm.com> 
wrote:
> Kevin,
>
> The FCP-4 working group is looking to find if the use of the parameter
> field (Frame Header parameter) is used in a consistent enough manner in
> the LS_ACC to a REC ELS to state in FCP-4 what it should be set to.  My
> response was to state what IBM tape drives put in this field.
>
> Thanks,
>
> Kevin D. Butt
> SCSI & Fibre Channel Architect, Tape Firmware
> MS 6TYA, 9000 S. Rita Rd., Tucson, AZ 85744
> Tel: 520-799-5280
> Fax: 520-799-2723 (T/L:321)
> Email address: kdbutt at us.ibm.com
> http://www-03.ibm.com/servers/storage/
>
>
>
> From:
> "Kevin Jones" <kev at bri.hp.com>
> To:
> Kevin D Butt/Tucson/IBM at IBMUS, t10 at t10.org
> Cc:
> bob.nixon at emulex.com
> Date:
> 03/17/2009 08:25 AM
> Subject:
> Re: REC ELS parameter field
>
>
>
> I'm confused.
>
> Are we talking about to REC.LS_ACC.Word5 (Frame header parameter)
> or REC.LS_ACC.Word10 (Frame Payload FC4VALUE) see FCP4 section 6.5 ?
>
> HP LTO drives set REC.LS_ACC.Word5 = 0.
> HP LTO drives set REC.LS_ACC.Word10 = bytes read/written.
>
>
> Kevin Jones
>
> 
===========================================================================
> Hewlett-Packard Limited registered Office:
> Cain Road, Bracknell, Berks RG12 1HN
> Registered No: 690597 England
>
> The contents of this message and any attachments to it are confidential
> and may be legally privileged. If you have received this message in 
error,
> you should delete it	from your system immediately and advise the 
sender.
>
> To any recipient of this message within HP, unless otherwise
> stated you should consider this message and attachments as
> "HP CONFIDENTIAL".
>
>
>
> On Tue, 17 Mar 2009 14:23:52 -0000, Kevin D Butt <kdbutt at us.ibm.com>
> wrote:
>
>> In response to the question sent on the reflector:
>>
>> FCP-4 folks: FC-LS requires that ?The value of the Parameter field in
> the
>> Frame_Header of an REC ELS and an LS_ACC in response to an REC ELS 
shall
>> be specified by the FC-4 that sends the frame.? FCP-4 specifies the
> value
>> of the Parameter field for the ELS but not for the LS_ACC.
>> What do people actually do for the LS_ACC? Is it consistent enough to 
say
>> something in FCP-4?
>>
>>
>> The parameter field of LS_ACC is the same as the parameter field of REC
>> ELS, unless an error occurs internal to the tape drive which requires
> the
>> entire command to be redriven.  In that case, the parameter field of 
the
>> LS_ACC is set to zero to indicate an FCP_RO of zero.  The intent is for
>> the initiator port to discard any previously received data and redrive
> the
>> command by sending an SRR with a relative offset of zero.
>>
>> Kevin D. Butt
>> SCSI & Fibre Channel Architect, Tape Firmware
>> MS 6TYA, 9000 S. Rita Rd., Tucson, AZ 85744
>> Tel: 520-799-5280
>> Fax: 520-799-2723 (T/L:321)
>> Email address: kdbutt at us.ibm.com
>> http://www-03.ibm.com/servers/storage/



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