7/95 FC-AL Direct Attach Disk Adhoc Minutes

Kurt Chan kc at core.rose.hp.com
Tue Jul 11 17:56:31 PDT 1995


From:  Kurt Chan , HP
To:    FC, SCSI Reflectors 
Subj:  7/95 FC-AL Direct Attach Disk Adhoc Minutes
Date:  7/11/95 
 
               FC-AL Direct Attach Disk Adhoc Meeting Minutes
                          Colorado Springs, CO
                               7/10/95     

    Dal Allan         ENDL             dal.allan at mcimail.com 
    Charles Binford   Symbios Logic    charles.binford at symbios.com
    Kurt Chan         HP Roseville     kc at core.rose.hp.com
    Mike Chenery      Fujutsu          mchenery at fcpa.fujitsu.com
    Jim Coomes        Seagate          jim_coomes at notes.seagate.com
    Tom Coughlan      Digital          coughlan at star.enet.dec.com
    Edward Fong       Amdahl           edward_fong at spg.amdahl.com
    Giles Frazier     IBM              gfrazier at ausvm6.vnet.ibm.com
    Gene Freeman      Symbios Logic    gene.freeman at symbios.com
    Ed Gardner        Quantum          gardner at acm.org
    Doug Hagerman     Digital          hagerman at starch.enet.dec.com
    Norm Harris       Adaptec          nharris at eng.adaptec.com
    Bill Hutchison    HP               hutch at boi.hp.com
    Skip Jones        Qlogic           sk_jones at qlc.com
    Jean Kodama       QLogic           j_kodama at qlc.com
    Mark Lewis        Digital          lewis at ssdevo.enet.dec.com
    Gene Milligan     Seagate          gene_milligan at notes.seagate.com
    Charles Monia     Digital          monia at shr.dec.com
    Al Pease          Buslogic         alp at buslogic.com
    Jim Pherson       Digital          pherson at ssdevo.enet.dec.com
    Lansing Sloan     LLNL             ljsloan at llnl.gov
    Bob Snively       Sun              bob.snively at sun.com
    Arlan Stone       Unisys           arlan.stone at mv.unisys.com
    Horst Truestedt   IBM              truested at vnet.ibm.com
    Michael Walker    Digital          walker at peaks.enet.dec.com
    Stewart Wyatt     HP DMD           stewart at hpbs3928.boi.hp.com
    Anthony Yang      Hitachi          yang_a at halsp.hitachi.com


1. SCHEDULE

   There are no future FC-AL direct attach disk adhoc meetings scheduled.
   The next two FC-AL2 meetings will be held Friday mornings of X3T11 weeks:

                 Fri 8/11, 830am   Tarrytown, NY
                 Fri 10/6, 830am   Toronto

   The Monday slot during X3T10 weeks will no longer be used for either
   profile or FC-AL meetings.


2. DOCUMENT LOGISTICS

   Revision 1.90 of the Direct Attach profile was distributed, and revision
   2.00 will be the version forwarded to X3T11 as a Technical Report (TR).
   The postscript for the profile is available via anonymous ftp on
   ftp.symbios.com unden pub/standards/io/fc/prv_*.ps.  Dal distributed
   copies of an X3T11 project proposal for creating the TR. 

   Any future discussions kegarding the profile will take place on the
   disk_attach reflector (disk_attach at dt.wdc.com).  To subscribe or
   unsubscribe, send email to majordomo at dt.wdc.com with a blank subject line
   and one of the following text lines:

		subscribe disk_attach your_email_address
		unsubscribe disk_attach your_email_address

   When posting to the reflector, please include a header which includes a
   "From:" and "To: disk_attach" field so those of us who subscribe to
   multiple reflectors know which reflector the posting is associated with.


3. TIMERS AND TIMEOUTS

   Version 1.90 reevaluates the timers needed for interoperability on private
   loops.  There are three "interface" times defined:

      A more liberal AL_TIME (called PL_TIME) was agreed upon which assumes
      an *average* inter-node cable segment length of 500m rather than 10km.
      This gives a total loop length of 67km (42 miles) for a 134-node loop
      rather than the unrealistic worst-case of 1,340km (837 miles) assumed
      by FC-AL.  As a result, PL_TIME is 1ms whereas AL_TIME is 15ms.

      LIS_HOLD_TIME was defined as the maximum amount of time a node shall
      hold a Loop Initialization Sequence before forwarding it to the next
      node.  The value chosen is 1ms.

      LM_TOV is the minimum amount of time the Loop Master waits for a Loop
      Initialization Sequence to be returned before assuming the loop is not
      functioning.  The value includes at least 126 AL_TIMEs and 126
      LIS_HOLD_TIMEs, and is chosen to be 300ms.

   There are 4 initiator times (in addition to a ULP timer):  AW_TIME,
   SRR_TIME, E_D_TOV, and R_A_TOV.

      AW_TIME is the minimum period of time an NL_Port shall wait to win
      arbitration before it may assume a malfunction or excessive unfairness.
      The value is 1 second, which takes into account 126 nodes all
      transmitting 64k bytes per loop tenancy at 266Mb/s, and each node
      unfairly arbitrating once in addition to its initial arbitration.

      SRR_TIME is the maximum time an Initiator assumes the Target will take
      to respond to a transfer of Sequence Initiative before invoking error
      recovery (after also taking into account physical propagation delay and
      arbitration time).  The value may be command-dependent,
      workload-dependent, and/or device-dependent.  Initiators may choose not
      to define this time specifically, but group it into a ULP timer.

      E_D_TOV is the minimum time an Initiator shall wait between the time it
      transmits a frame requesting transfer of Sequence Initiative and the
      time it receives a frame within the same Exchange which acknowledges
      the transfer of Sequence Initiative before invoking error recovery.  It
      includes at least one AW_TIME, one SRR_TIME, and two PL_TIMEs.  The
      value chosen is 2 seconds.  Initiators may elect not to define this
      specifically, but group it into a ULP timer.

      R_A_TOV is equal to zero since private loops cannot misorder frames.
      Following receipt of the ACC to ABTS, Initiators may immediately
      transmit RRQ.

      A ULP timeout value is the time between the ULP dispatches a SCSI
      command to the interface and the time the ULP receives SCSI status.
      It shall be greater than or equal to E_D_TOV.

   There is one Target timer:

      R_R_TOV is a resource recovery timer used by multi-initiator targets
      to reclaim resources which the target has dedicated to initiators
      which have since "failed."  It is the minimum time a target shall
      wait for:

      a) ADISC/PDISC from an initiator which has an open task, following 
         receipt of LIP, or
      b) an initiator response to a transfer of Sequence Initiative

      before implicitly logging out that initiator, unless an ACA condition
      is in effect for that initiator (in which case R_R_TOV is infinite).
      The value chosen is 2 seconds.


4. EXCHANGE AUTHENTICATION

   Rather than require Targets to originate ADISC or PDISC upon expiration
   of RR_TOV, the Targets will instead be required to:

    a) suspend all open tasks until the initiators with open tasks complete
       the ADISC/PDISC authentication protocol, and

    b) implicitly log out any initiators which do not send an ADISC or
       PDISC no earlier than RR_TOV after the target receives a LIP.  


5.  LOGIN VALIDATION AND IMPLICIT LOGOUT

    The examples for login validation were clarified to require that when an
    ADISC or PDISC is sent to a target, all three identifiers (Port name,
    Node name, N_Port ID) must match a logged in initiator in the target or
    else LOGO will be returned to the initiator in response to the ADISC or
    PDISC.

    If a target supports 'N' logins and receives an N+1'th PLOGI request, 

      a) if there were no open tasks with the least recently used initiator,
	 that initiator may be implicitly logged out.

      b) if there are open tasks with all 'N' initiators, the login
         request shall be returned with LS_RJT and reason code "unable to
         perform command request."


6. FCP_RSP PAYLOAD

   Single-lun targets are restricted to 128-byte FCP_RSP payloads.  Hosts
   which ONLY support single-lun direct access targets may rely on no
   FCP_RSP payload exceeding this value.  However, hosts which support
   other devices or device types (e.g., controller devices) must assume
   those devices can return the full 255 bytes permitted by SCSI-3.


7. ACA

   To remain consistent with the FCSI profiles, initiators are prohibited
   from requiring targets to implement ACA.  Prior to this, targets which
   did not implement ACA and Initiators which required it could not
   interoperate.  Other profile may have additional requirements regarding
   host notification of configuration or logical block size changes in
   order to preserve data integrity without the use of ACA (see FCSI SCSI
   profile).


8. MULTI-LUN DISK

   Some high-capacity (8+Gbyte) drives must use multiple LUNs in order to
   make full use of their capacity on some operating systems.  Charles
   Binford asked the question of where the LUN should be specified in the
   FCP_LUN field of the FCP_CMND payload.  The consensus was to use the
   "first level addressing" field in the SCC command set, and to report
   "peripheral device addressing method" (00b) per Table 5 in SCC.




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