Request for Comments: 4455 Sanrad Intelligent Storage
Category: Standards Track M. Bakke
Cisco Systems, Inc.
Y. Lederman
Siliquent Technologies
M. Krueger
Hewlett-Packard
K. McCloghrie
Cisco Systems, Inc.
April 2006
Definition of Managed Objects for Small Computer
System Interface (SCSI) Entities
Status of This Memo
This document specifies an Internet standards track protocol for the
Internet community, and requests discussion and suggestions for
improvements. Please refer to the current edition of the "Internet
Official Protocol Standards" (STD 1) for the standardization state
and status of this protocol. Distribution of this memo is unlimited.
Copyright Notice
Copyright (C) The Internet Society (2006).
Abstract
This memo defines a portion of the Management Information Base (MIB),
for use with network management protocols in the Internet community.
In particular, it describes managed objects for Small Computer System
Interface (SCSI) entities, independently of the interconnect
subsystem layer.
Table of Contents
1. The Internet-Standard Management Framework ......................3
2. Requirements Notation ...........................................3
3. Overview ........................................................3
3.1. Introduction ...............................................4
3.2. SCSI Terminology ...........................................6
3.2.1. SCSI Application Layer ..............................6
3.2.2. SCSI Device .........................................6
3.2.3. SCSI Port ...........................................6
3.2.4. SCSI Initiator Device ...............................7
3.2.5. SCSI Initiator Port .................................7
3.2.6. SCSI Target Device ..................................7
3.2.7. SCSI Target Port ....................................7
3.2.8. Logical Units .......................................7
3.2.9. Logical Unit Number .................................7
3.2.10. Interconnect Subsystem .............................7
3.2.11. Device Server ......................................8
3.2.12. Task Manager .......................................8
3.2.13. SCSI Instance ......................................8
3.3. SCSI MIB Module Implementation .............................8
3.4. Bridging and Virtualization ...............................10
3.5. SCSI Command MIB Module ...................................11
4. Structure of the MIB ...........................................11
4.1. The SCSI Device Group .....................................11
4.2. The Initiator Group .......................................11
4.3. The Target Group ..........................................11
4.4. The Discovery Group .......................................12
4.5. The LUN Map Group .........................................12
4.6. The Target Statistic Group ................................12
4.7. The Target High Speed Statistic Group .....................12
4.8. The LUN Map Statistics Group ..............................12
4.9. The LUN Map Statistics High Speed Group ...................13
4.10. The Initiator Statistics Group ...........................13
4.11. The Initiator High Speed Statistic Group .................13
4.12. The Discovery Statistics Group ...........................13
4.13. The Discovery Statistics High Speed Group ................14
4.14. The Device Statistics Group ..............................14
5. Relationships in This MIB ......................................14
6. Relationship to Other MIBs .....................................16
6.1. Host Resource MIB .........................................16
6.2. iSCSI MIB Module ..........................................16
7. Miscellaneous Details ..........................................16
7.1. Names and Identifiers .....................................16
7.2. Logical Unit Number .......................................16
7.3. Notifications .............................................16
7.4. SCSI Domains ..............................................17
7.5. Counters: 32 Bits and 64 Bits .............................17
7.6. Local versus Remote Entities ..............................18
8. Abbreviations ..................................................18
9. Object Definitions .............................................18
10. Object Population Example: SCSI Target and Initiator
Devices on a pSCSI Bus ........................................76
10.1. scsiInstance Table: ......................................77
10.2. scsiDevice Table: ........................................77
10.3. scsiPort Table: ..........................................77
10.4. scsiTransport Table: .....................................77
10.5. scsiIntrDev Table: .......................................78
10.6. scsiInitiatorPort Table: .................................78
10.7. scsiDscTgt Table: ........................................78
10.8. scsiDscLUN: ..............................................78
10.9. scsiDscLUNIdentifier: ....................................79
10.10. scsiAttTgtPort Table: ...................................79
10.11. scsiTgtDev Table: .......................................79
10.12. scsiTgtPort Table: ......................................80
10.13. scsiLU Table: ...........................................80
10.14. scsiLuId Table: .........................................80
10.15. scsiLunMap Table: .......................................81
10.16. scsiAuthorizedIntr Table: ...............................81
10.17. scsiAttIntrPort Table: ..................................81
11. Security Considerations .......................................81
12. Acknowledgements ..............................................84
13. IANA Considerations ...........................................84
14. References ....................................................84
14.1. Normative References .....................................84
14.2. Informative References ...................................85
1. The Internet-Standard Management Framework
For a detailed overview of the documents that describe the current
Internet-Standard Management Framework, please refer to section 7 of
RFC 3410 [RFC3410].
Managed objects are accessed via a virtual information store, termed
the Management Information Base or MIB. MIB objects are generally
accessed through the Simple Network Management Protocol (SNMP).
Objects in the MIB are defined using the mechanisms defined in the
Structure of Management Information (SMI). This memo specifies a MIB
module that is compliant to the SMIv2, which is described in STD 58,
RFC 2578 [RFC2578], STD 58, RFC 2579 [RFC2579] and STD 58, RFC 2580
[RFC2580].
2. Requirements Notation
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119].
3. Overview
This memo defines a portion of the Management Information Base (MIB)
for use with network management protocols in the Internet community.
In particular, it describes a set of managed objects to configure and
monitor Small Computer System Interface entities (SCSI entities),
i.e., SCSI target devices and SCSI initiator devices and SCSI ports.
SCSI is a client-server protocol in which application clients within
a SCSI initiator device (client) issue service requests to logical
units contained in a SCSI target device(server).
This MIB module is based on documents defined by the ANSI T10
Technical Committee, specifically the SCSI Architecture Model - 2
[SAM2] and SCSI Primary Commands - 2 [SPC2].
The [SAM2] standard is the primary source for the SCSI architecture
discussion in this document and the terminology used in this MIB
module.
3.1. Introduction
In the late 1970s, a firm called Shugart Associates started to have
some considerable success with a peripheral interface definition in
what became the PC marketplace, and this interface was adopted and
extended by an open standards committee to form the Small Computer
Systems Interface (SCSI). SCSI defines an 8-bit-wide multi-drop
"bus" structure, which could interconnect a total of eight
peripherals and computer systems.
It is important to realize that initially SCSI standardized only the
"physical connection", i.e., the connectors, cables, and interface
signals. Thus, even though a peripheral could be connected to
multiple systems, the information that flowed across the interface
was different in each case. This was addressed some five years later
by the definition of a Common Command Set, and with this definition
in place it was possible for the first time to develop a peripheral
with both a common interface and common operating firmware for
connection to multiple systems.
The physical interface of SCSI continued to be developed throughout
the 1980s with the addition of fast (up to 10 megabytes/s) and wide
(16 bits) variants, but the distance supported remained a maximum of
25 meters (from one end of the bus to another), and indeed some of
the faster variants supported much less than that distance. The
command set development continued, with special commands for tapes,
printers, and even processors being added to the original disk-
oriented set. So successful was SCSI in the 1980s that the majority
of the available Operating Systems incorporated support for the SCSI
command set as standard.
However, at the end of the 1980s the distance, speed, and number of
devices supported by SCSI were starting to become significant
impediments to systems design, and although the "information
explosion" had not yet started in earnest, it was already being
anticipated. At the same time, the serial interface technologies
developed for Local Area Networks such as Ethernet, and the fibre
optics technologies that were first deployed in telecommunications
applications were starting to appear sufficiently rugged and low cost
for use in peripheral interface applications. Thus, a standards
project was begun in 1988 to develop a new serial, fibre-optic
interface to carry the SCSI command sets and other peripheral
protocols. This interface eventually became known as Fibre Channel
(FC), and it is based on an architecture centered around an
abstractly defined "fabric", which may be a switch or a loop
connection. MIB modules for various FC equipments are already in
existence.
In order to support the new interfaces, it was necessary to
completely reorganize the SCSI standards and definitions. The
command sets were separated from the physical interface definitions,
and a SCSI Architectural Model (SAM) was created to define the
interaction between the various standards. It is a key to
understanding SAM to realize that it was first created approximately
10 years AFTER the first SCSI products were shipped!
The most recent development in this saga occurred in 2000 when an
IETF Working Group was formed to address, among other things, a
definition for transporting the SCSI command sets directly over a
TCP/IP infrastructure. This effort is known as iSCSI [RFC3720], and
an iSCSI MIB module is already under development [ISCSI].
Most of the projects are in T10, except Fibre Channel, which is
defined by T11 and IEEE defines 1394.
The SCSI MIB module represents the SCSI protocol layer common to all
SCSI command sets and transports. It does not represent the command
sets and transports themselves. These should appear in other MIB
modules specific to the transport or command set. The following
illustration shows the relationships between the various actual and
possible SCSI-related MIB modules.
+---------------------------------+
SCSI Command | Higher-level MIBs, specific to |
Sets | command sets, disk, tape, etc. |
+---------------------------------+
SCSI | SCSI MIB |
+-------+---------+-------+-------+
SCSI | iSCSI | FCP | SPI | Other |
Transport | MIB | MIB | MIB | MIBs |
Protocols | | | | |
+-------+---------+-------+-------+
SCSI | TCP | Fibre | Other |
Interconnect | MIB | Channel | Interconnect |
| | MIBs | MIBs |
+-------+---------+---------------+
An iSCSI MIB module [ISCSI] and a Fibre Channel interconnect MIB
module [RFC4044] are currently being developed. No development is
currently planned for standard command-set-specific or device-
specific MIBs.
The TCP-MIB [RFC4022] is already a proposed standard RFC 4022.
3.2. SCSI Terminology
The following sections explain some of the SCSI terminology, which is
used later in defining the MIB module. For the authoritative
definitions of these terms, see SAM-2 [SAM2].
3.2.1. SCSI Application Layer
The protocols and procedures that implement or invoke SCSI commands
and task management functions by using services provided by a SCSI
transport protocol layer.
3.2.2. SCSI Device
A SCSI device is an entity that contains one or more SCSI ports that
are connected to a service delivery subsystem and supports a SCSI
application protocol.
3.2.3. SCSI Port
A SCSI port is a device-resident entity that connects the application
client, device server, or task manager to the service delivery
subsystem through which requests and responses are routed. A SCSI
port is synonymous with port and either a SCSI initiator port or a
SCSI target port.
3.2.4. SCSI Initiator Device
A SCSI initiator device contains application clients and SCSI
initiator ports that originate device service and task management
requests to be processed by a SCSI target device. When used, this
term refers to SCSI initiator devices or SCSI target/initiator
devices that are using the SCSI target/initiator port as a SCSI
initiator port.
3.2.5. SCSI Initiator Port
A SCSI initiator port acts as the connection between application
clients and the service delivery subsystem through which requests and
responses are routed. In all cases when this term is used, it refers
to an initiator port or a SCSI target/initiator port operating as a
SCSI initiator port.
3.2.6. SCSI Target Device
A SCSI target device contains logical units and SCSI target ports
that receive device service and task management requests for
processing. When used, this term refers to SCSI target devices or
SCSI target/initiator devices that are using the SCSI
target/initiator port as a SCSI target port.
3.2.7. SCSI Target Port
A SCSI target port contains a task router and acts as the connection
between device servers and task managers and the service delivery
subsystem through which requests and responses are routed. When this
term is used, it refers to a SCSI target port or a SCSI
target/initiator port operating as a SCSI target port.
3.2.8. Logical Units
A logical unit is an entity residing in the SCSI target device that
implements a device model and processes SCSI commands sent by an
application client.
3.2.9. Logical Unit Number
A Logical Unit Number or LUN is a 64-bit identifier for a logical
unit.
3.2.10. Interconnect Subsystem
An interconnect subsystem is one or more interconnects that appear as
a single path for the transfer of information between SCSI devices.
3.2.11. Device Server
A device server is an object within the logical unit that processes
SCSI tasks according to the rules for task management.
3.2.12. Task Manager
A task manager is a server within the SCSI target device that
processes task management functions.
3.2.13. SCSI Instance
A "SCSI instance" is a distinct SCSI entity within a managed system.
Whereas most implementations will have just one SCSI instance, the
MIB module allows for multiple (virtual) instances, such that a large
system can be "partitioned" into multiple, distinct virtual systems.
For example, in a host, it allows multiple vendors’ implementations
of the MIB module to co-exist under a single SNMP agent through each
vendor’s implementation being a different SCSI instance. It also
allows a single SNMP agent to represent multiple subsystems each of
which has its own SCSI instance.
3.3. SCSI MIB Module Implementation
The SCSI MIB module is a basic building block to use in the various
SCSI management scenarios. This module is intended to be implemented
in every SCSI entity in a managed system. A SCSI entity can be a
SCSI initiator device, SCSI target device or SCSI initiator and
Target device. Since SCSI (storage) networking devices may contain
more than one SCSI entity, it is possible that more than one SCSI
instance will reside in a single device.
In small-scale environments, a single network management station
(NMS) may have SNMP access to both SCSI initiator devices and SCSI
target devices. However, if the SCSI target devices, or virtualized
target devices, are being provided as a service, it is more likely
that the provider of the service owns and manages the SCSI target
devices and that the consumer of the service owns and manages the
SCSI initiator devices. In this case, the service provider NMS and
the consumer NMS may have only allowed SNMP access to the SCSI target
devices and the SCSI initiator devices, respectively.
The figures in this chapter describe the location of the SCSI MIB
module implementations in the various SCSI management scenarios. The
locations of the SCSI SNMP agent implementing the SCSI MIB module are
denoted with ’*’.
+----------+ +---------+
|SCSI | SCSI Transport |SCSI |
|Initiator +---------------------------------------+Target |
|Device | |Device |
| * | | * |
+----------+ +---------+
| |
| |
| |
| |
| |
| SNMP +----------+ SNMP |
+------------------|SCSI |-------------------+
|Management|
| (NMS) |
+----------+
Figure 1. Single SCSI Initiator Device and
Single SCSI Target Device
Figure 1 describes a simple SCSI management scenario of a SCSI
initiator device, a SCSI target device, and a management station. In
this scenario, there are two SNMP agents, each containing its SCSI
instance and its respective objects. As the SCSI target device and
SCSI initiator device are interconnected, their target and initiator
port objects will be complementary.
+-----------+
| +--------+-+ SCSI Transport +---------+
| | SCSI |---------------------------------------+ SCSI |
|* | Initiator+---------------------------------------+ Target |
+--| Device | SCSI Transport | Device |
| | * | | * |
| +----------+ +---------+
| | |
| | |
| | |
| | |
| | |
|SNMP | SNMP +----------+ SNMP |
+-------+------------------|SCSI |-------------------+
|Management|
| (NMS) |
+----------+
Figure 2. Multiple Hosts and a Single Target Device