SCSI WORKING DOCUMENT X3T9.2/89-133 R03 Date : September 6, 1990 To : John Lohmeyer, Chairman, X3T9.2 From : Gary R. Stephens IBM Corporation D67E/060-1 9000 S. Rita Rd. Tucson, Az 85719 (602) 799-2246 Subject: Logical Model for SCSI-3 Parallel Busses The attached document is a draft of the logical model limited to SCSI-3 Parallel busses. All operations required only on the Fiber Channel have been moved to X3T9.3/90-132 R01. The terminology is consistent with the full logical operation model. The work group attendees decided to attempt a split between SCSI-2-like parallel bus operations and a Fiber Channel mapping on parallel busses. The plenary is asked to define a separate project proposal, being written by Dal Allan, for the Fiber Channel SCSI definition. This version has eliminated all provisions for the multiple port operations required for full Fiber Channel operation. The dual port feature for SCSI-3 Parallel busses is introduced. (See X3T9.2/90-136 R00, Gerry Houlder, Seagate). Note that the dual port provisions will not be carried forward into the Fiber Channel operations model mapped to a parallel bus. The concepts in the model are presented in a form similar to the models developed for the various device classes. This format provides a structure to name the concepts and functions and present them in a logical sequence. The logical model is proposed for addition to Section 6 of the SCSI standard. Some glossary terms are proposed for addition to Section 3.1. Gary R. Stephens 1 SCSI WORKING DOCUMENT X3T9.2/89-133 R03 2 SCSI-3 ADDITIONS for Logical Operations Model(Parallel) SCSI WORKING DOCUMENT X3T9.2/89-133 R03 3.1. Glossary (Addendum) dual port. An implementation of an initiating controller or target controller which has exactly two ports. No cooperation between the ports on either an initiating controller or target controller occurs during an I/O process. ICID. initiating controller ID. initiating controller. A logical element which principally starts I/O processes. I/O processes execute using the services of one port in initiator mode. An initiating controller may have one or two ports acting as initiators (see dual port). initiating controller ID. An identifier assigned to each initiating controller. initiator. An SCSI device, operating in initiator mode, through which an initiating controller starts I/O processes. An initiator usually attaches to an initiating controller. An initiator is a port to one SCSI bus. port. A port is the name for the portion of an SCSI device where it attaches to one SCSI bus. An SCSI device may have more than one port. (See dual port.) Each port may attach to a different SCSI bus. Each port has an SCSI ID and an SCSI address unique to the SCSI bus to which it attaches. Ports function as initiators and/or targets. port number. A unique number assigned to each port on a target controller or initiating controller. target. An SCSI device, operating in target mode, thorough which I/O processes pass for execution by a target controller, Logical Unit, or target routine. An target usually attaches to an target controller. A target is a port to one SCSI bus. target controller. A logical element which principally executes I/O processes. I/O processes execute using the services of one port in target mode. A target controller may have one or two targets (see dual port). target routine. An addressable function within a target controller which executes I/O processes. A target routine is similar to a logical unit in that it has a name, a target routine number or TRN, and a command set to execute. target routine number. The name of a target routine used during an I/O process to select a target controller function to execute an I/O process. 3 SCSI WORKING DOCUMENT X3T9.2/89-133 R03 4 SCSI-3 ADDITIONS for Logical Operations Model(Parallel) SCSI WORKING DOCUMENT X3T9.2/89-133 R03 6.1. Logical Operation Model for Parallel Busses The logical operation model describes device-independent activity using one or two SCSI ports per initiating controller or target controller. The next section provides a glossary related to the logical operations model. The glossary is followed by the logical operation model description. 6.1.1 Glossary for Logical Operation Model implicitly named path. A path with no explicit ICID or initiating controller port number transferred from an initiating controller to any LUN or TRN on a target controller from the path where the connect was made and, the initiating controller does not receive the port number from the target controller. logical path. A logical path is the set of all paths having the same ICID and LUN or TRN in the same target controller indicating routes I/O processes may take between an initiating controller and a logical unit or target routine. path. A path is a named physical link between an initiating controller and a logical unit or target routine. At least one connect has been made from the initiating controller to the logical unit or target routine. ungrouped. The state of a path when it is an implicitly named path. 5 SCSI WORKING DOCUMENT X3T9.2/89-133 R03 Attributes of a Minimum Logical System Initiating Controller ICID Initiating Controller Port Number SCSI Address SCSI ID Port --------- SCSI Bus ---------- Port (Initiator Mode) (Target Mode) Initiator Target SCSI Address SCSI ID Target Controller Port Number Target Controller Logical Unit LUN +-----+ +-----+ | | | | | P | | P | | O |----------------------------| O | | R | | R | | T | SCSI Bus | T | | | | | +-----+ +-----+ Path = ICID || Initiating Controller Port Number || Initiator SCSI Address || Target SCSI Address || Target Controller Port Number || LUN Path implicitly named Path in the Ungrouped State Note: || means concatenated with Figure 6.c. MINIMUM LOGICAL SYSTEM ATTRIBUTES 6 SCSI-3 ADDITIONS for Logical Operations Model(Parallel) SCSI WORKING DOCUMENT X3T9.2/89-133 R03 6.1.2. Logical Operation Model Description A logical system consists fifteen (15) items as follows: 1) a minimum of two SCSI ports and one SCSI bus connecting them; a maximum two SCSI busses with a minimum of four SCSI ports, two on each SCSI bus; the maximum number of SCSI ports is determined by the physical bus characteristics; 2) a minimum of one SCSI port must be capable of operating in initiator mode (called an initiator) on each SCSI bus; 3) a minimum of one SCSI port must be capable of operating in target mode (called a target) on each SCSI bus; 4) the initiator and target in 2) and 3) above, attached to the same SCSI bus and are active in their respective modes during a connection between them (i.e., not the same port); 5) the logical element attaching an SCSI device which principally starts I/O processes is called an initiating controller. An initiating controller has one port and a maximum of two ports (called dual ports). 6) the logical element attaching an SCSI device which principally receives and executes I/O processes is called a target controller. A target controller has one port and a maximum of two ports (called dual ports). A minimum dual port logical system consists of one initiating controller with two ports or two initiating controllers with one port each one target controller with two ports connected by two SCSI busses as in item 4). NOTE: A dual port logical system provides an alternate physical path from the initiating controller to the target controller. 7) each port has an SCSI address unique to the SCSI bus on which it is attached; the SCSI address translates to the physical SCSI ID on a parallel SCSI bus. The SCSI addresses may be the same or different for each port when the ports attach to different SCSI busses. 8) each port, has a port number assigned by its controlling logical element. The port number is unique within a controlling logical element. 9) each target controller has one or more logical units each identified by a unique logical unit number (LUN). 10) each target controller has zero or more target routines each identified by a target routine number (TRN). 11) the extent of a logical system, from a target controller, is the set of all initiating controller/initiator combinations attached to the target controller and from which a connect has been made. For an initiating controller, the extent of a logical system is the set of all logical units and target routines to which a connect has been made. 7 SCSI WORKING DOCUMENT X3T9.2/89-133 R03 12) each initiating controller is assigned an initiating controller ID. An initiating controller ID (ICID) must be unique in a logical system; 13) An identifier consisting of a ICID, an initiating controller port number, an initiator SCSI address, a target controller SCSI address, a target controller port number, and a LUN or TRN, defines a path when the relationship is established as the result of a connect started by an initiating controller to a logical unit or target routine. This is called an implicitly named path. The LUN or TRN must be valid for the target controller. The logical unit need not be ready or installed (e.g., powered off but cabled or not cabled). No path exists between a LUN or TRN and an initiating controller unless the LUN or TRN is explicitly the object of a connect started by that initiating controller to the LUN or TRN. An implicitly named path exists when no explicit ICID or initiating controller port number has been transferred from an initiating controller to any LUN or TRN on this target controller on the path where the connect was made and, the initiating controller does not receive the port number from the target controller. NOTES: 1) If the ICID, initiating controller port number, and target controller port numbers were transferred between the logical elements then, the path is called an explicitly named path. 2) A connect using Asynchronous Event Notification does not define a path from the initiating controller to the logical unit or target routine. The logical unit or target routine must be selected as the receiver of an I/O process by the initiating controller. AEN uses the SCSI bus between the target controller, with one port in initiator mode, and a initiating controller, with one port in target mode. From the target controller, an implicit path is the result of the successful connect from the target controller to the initiating controller. 14) An identifier, consisting of an ICID and either a LUN or TRN in the same target controller, represents one logical path. A logical path consists of a set of one or two paths. An initiating controller has one path and a maximum of two paths to each logical unit or target routine. The paths in a logical path are in an ungrouped state. When a path is in the ungrouped state, each I/O process is limited to operation on the path where the connect was made. The set of paths available in a logical path from an initiating controller to any one logical unit or target routine may be determined from the results of the INQUIRY command response data provided the data is unique to each logical unit or target routine. 15) Any logical unit or target routine is initially available to receive I/O processes from any initiating controller attached to the target controller. 8 SCSI-3 ADDITIONS for Logical Operations Model(Parallel) SCSI WORKING DOCUMENT X3T9.2/89-133 R03 Such unrestricted access may not be appropriate for environments with extensive multi-user access and/or data bases with sensitive information. It may be necessary to control access to a logical unit, target routine or an extent within a logical unit using the RESERVE/RELEASE functions. When a logical unit, target routine, or extent within a logical unit becomes reserved on one port of a target controller it becomes reserved to the path on the SCSI bus where the reservation was made. The target controller enforces the reservation for the second port in dual port target controllers. That is, initiating controllers on the second bus are restricted in the same way as any other initiating controller not holding a reservation on the first bus. Third party reservation is limited to a second path on the same SCSI bus where the reservation was made. There is no provision to extend third party reservation to a path on a second port. 9 SCSI WORKING DOCUMENT X3T9.2/89-133 R03 END OF DOCUMENT X3T9.2/89-133 R03 10 SCSI-3 ADDITIONS for Logical Operations Model(Parallel)