[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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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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