[T11.3] E_D_TOV and tape drives
RogerR at exabyte.com
RogerR at exabyte.com
Tue Oct 29 14:24:27 PST 2002
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* RogerR at exabyte.com
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Per FC-FS rev 1.7 section 21.2.1.3 E_D_TOV only applies to "transmission of
consecutive Data frames within a single Sequence". The status is in a
different sequence from the command, so E_D_TOV doesn't apply.
This mechanism is also used to allow delays for draining or filling the
drive's buffer. The drive breaks up the transfer into multiple sequences.
Within each sequence, E_D_TOV applies, but between sequences the upper level
(SCSI) timeouts are the only limiting factor.
-roger rose
Exabyte Product Test Dept.
rogerr at exabyte.com
> -----Original Message-----
> From: Kevin D Butt [mailto:kdbutt at us.ibm.com]
> Sent: Tuesday, October 29, 2002 3:08 PM
> To: t10 at t10.org; t11_3 at mail.t11.org
> Subject: [T11.3] E_D_TOV and tape drives
>
>
> INCITS T11.3 Mail Reflector
> ********************************
> I have been looking at the following regarding E_D_TOV and have some
> confusion regarding tape drives. As I understand these
> references when a
> host issues a command (say a rewind) the target must respond within
> E_D_TOV. That means that a tape drive has to respond to a
> rewind within
> E_D_TOV (default of 2 seconds). Obviously, a tape drive
> cannot do this
> using the default value of E_D_TOV. There are other cases,
> including data
> transfer where 2 seconds is an unreasonable expectation.
> Does this force
> tape drives to modify their E_D_TOV to their longest SCSI
> command timeout
> value? This would be for a long Erase which can be on the order of a
> couple of hours.
>
> This would surely have some pretty odd effects on other
> timeouts and in my
> opinion, make for an extremely difficult multi-initiator environment.
>
> Do the standards really indicate that a target must give status to a
> command within E_D_TOV? Has this been addressed before?
>
> FCFS Rev 1.7a
>
> 21.2.1.3 E_D_TOV
> A short timeout value is known as the Error_Detect_Timeout
> Value (E_D_TOV).
> The E_D_TOV is used as the
> timeout value for detecting an error condition. The value of E_D_TOV
> represents a timeout value for detection of a
> response to a timed event. (i.e., during Data frame transmission it
> represents a timeout value for a Data frame to
> be delivered, the destination Nx_Port to transmit a
> Link_Response, and the
> Link_Response to be delivered to the
> Sequence Initiator.) The E_D_TOV value selected should consider
> configuration and Nx_Port processing param-eters.
> The default value is 2 seconds. However, a valid E_D_TOV
> value shall also
> adhere to the proper
> relationship to the R_A_TOV value. When an Nx_Port performs
> Fabric Login,
> the Common Service Parameters
> provided by the Fx_Port specify the proper value for E_D_TOV.
> When an Nx_Port performs N_Port Login in a point-to-point
> topology, the
> Common Service Parameters provided
> by each Nx_Port specify a value for E_D_TOV. If the two
> values differ, each
> Nx_Port shall use the longer time. An
> FC_Port may determine another FC_Port's value for E_D_TOV via the Read
> Timeout Value (RTV) ELS (see
>
>
> FCP 2r07a
> 11.6 Upper Level Protocol Time-out (ULP_TOV)
> ULP_TOV is an operation-specific timer maintained by the Upper Level
> Protocol. ULP_TOV is used to time the
> completion of Exchanges associated with ULP operations. Since
> the amount of
> time required varies depending
> upon the operation, the value assigned for this timer is
> determined by the
> operation being timed. Some
> operations may require extended periods of time to complete.
> ULP timers take into account response time increments caused
> by command
> queuing and multi-initiator
> congestion
>
> 11.2 Error_Detect Time-out (E_D_TOV)
> E_D_TOV is a general error detect time-out value. Its use is
> specified in
> FC-FS, FC-AL, FC-PLDA, FC-FLA, and
> FC-TAPE. For FCP-2 Sequence recovery, it is used to time the
> following:
> a) the maximum time permitted for a Sequence Initiator between the
> transmission of consecutive data
> frames within a single Sequence;
> b) the minimum time that a Sequence Recipient shall wait for
> the reception
> of the next frame within a single
> Sequence before recognizing a Sequence time-out; and
> c) the minimum time a Sequence Initiator shall wait for an
> ACK response
> before it considers the ACK to be
> missing and begins recovery actions.
>
> Thanks,
>
> Kevin D. Butt
> Fibre Channel & SCSI Architect
> IBM Tape Microcode,
> 6TYA, 9000 S. Rita Rd., Tucson, AZ 85744
> Tie-line 321; Office: 520-799-5280, Lab: 799-2869, Fax:
> 799-4138, Email:
> kdbutt at us.ibm.com
>
>
>
> To Unsubscribe:
> mailto:t11_3-request at mail.t11.org?subject=unsubscribe
>
>
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RE: [T11.3] E_D_TOV and tape drives
Per FC-FS rev 1.7 section 21.2.1.3 E_D_TOV only = applies to "transmission of consecutive Data frames within a = single Sequence". The status is in a different sequence from = the command, so E_D_TOV doesn't apply.
This mechanism is also used to allow delays for = draining or filling the drive's buffer. The drive breaks up the = transfer into multiple sequences. Within each sequence, E_D_TOV = applies, but between sequences the upper level (SCSI) timeouts are the = only limiting factor.
-roger rose
Exabyte Product Test Dept.
rogerr at exabyte.com
> -----Original Message-----
> From: Kevin D Butt [<3d.htm>mailto:kdbutt at us.ibm.com]
> Sent: Tuesday, October 29, 2002 3:08 PM
> To: t10 at t10.org; t11_3 at mail.t11.org
> Subject: [T11.3] E_D_TOV and tape drives
>
>
> INCITS T11.3 Mail Reflector
> ********************************
> I have been looking at the following regarding = E_D_TOV and have some
> confusion regarding tape drives. As I = understand these
> references when a
> host issues a command (say a rewind) the target = must respond within
> E_D_TOV. That means that a tape drive has = to respond to a
> rewind within
> E_D_TOV (default of 2 seconds). = Obviously, a tape drive
> cannot do this
> using the default value of E_D_TOV. There = are other cases,
> including data
> transfer where 2 seconds is an unreasonable = expectation.
> Does this force
> tape drives to modify their E_D_TOV to their = longest SCSI
> command timeout
> value? This would be for a long Erase = which can be on the order of a
> couple of hours.
>
> This would surely have some pretty odd effects = on other
> timeouts and in my
> opinion, make for an extremely difficult = multi-initiator environment.
>
> Do the standards really indicate that a target = must give status to a
> command within E_D_TOV? Has this been = addressed before?
>
> FCFS Rev 1.7a
>
> 21.2.1.3 E_D_TOV
> A short timeout value is known as the = Error_Detect_Timeout
> Value (E_D_TOV).
> The E_D_TOV is used as the
> timeout value for detecting an error condition. = The value of E_D_TOV
> represents a timeout value for detection of = a
> response to a timed event. (i.e., during Data = frame transmission it
> represents a timeout value for a Data frame = to
> be delivered, the destination Nx_Port to = transmit a
> Link_Response, and the
> Link_Response to be delivered to the
> Sequence Initiator.) The E_D_TOV value selected = should consider
> configuration and Nx_Port processing = param-eters.
> The default value is 2 seconds. However, a = valid E_D_TOV
> value shall also
> adhere to the proper
> relationship to the R_A_TOV value. When an = Nx_Port performs
> Fabric Login,
> the Common Service Parameters
> provided by the Fx_Port specify the proper = value for E_D_TOV.
> When an Nx_Port performs N_Port Login in a = point-to-point
> topology, the
> Common Service Parameters provided
> by each Nx_Port specify a value for E_D_TOV. If = the two
> values differ, each
> Nx_Port shall use the longer time. An
> FC_Port may determine another FC_Port's value = for E_D_TOV via the Read
> Timeout Value (RTV) ELS (see
>
>
> FCP 2r07a
> 11.6 Upper Level Protocol Time-out = (ULP_TOV)
> ULP_TOV is an operation-specific timer = maintained by the Upper Level
> Protocol. ULP_TOV is used to time the
> completion of Exchanges associated with ULP = operations. Since
> the amount of
> time required varies depending
> upon the operation, the value assigned for this = timer is
> determined by the
> operation being timed. Some
> operations may require extended periods of time = to complete.
> ULP timers take into account response time = increments caused
> by command
> queuing and multi-initiator
> congestion
>
> 11.2 Error_Detect Time-out (E_D_TOV)
> E_D_TOV is a general error detect time-out = value. Its use is
> specified in
> FC-FS, FC-AL, FC-PLDA, FC-FLA, and
> FC-TAPE. For FCP-2 Sequence recovery, it is = used to time the
> following:
> a) the maximum time permitted for a Sequence = Initiator between the
> transmission of consecutive data
> frames within a single Sequence;
> b) the minimum time that a Sequence Recipient = shall wait for
> the reception
> of the next frame within a single
> Sequence before recognizing a Sequence = time-out; and
> c) the minimum time a Sequence Initiator shall = wait for an
> ACK response
> before it considers the ACK to be
> missing and begins recovery actions.
>
> Thanks,
>
> Kevin D. Butt
> Fibre Channel & SCSI Architect
> IBM Tape Microcode,
> 6TYA, 9000 S. Rita Rd., Tucson, AZ = 85744
> Tie-line 321; Office: 520-799-5280, Lab: = 799-2869, Fax:
> 799-4138, Email:
> kdbutt at us.ibm.com
>
>
>
> To Unsubscribe:
> <3d.htm>mailto:= t11_3-request at mail.t11.org?subject=3Dunsubscribe
>
>
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