RFC 4455
Definition of Managed Objects for Small Computer System Interface (SCSI) Entities
Network Working Group M. Hallak-Stamler 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
Figure 2 adds another SCSI initiator device, to the SCSI network, which connects to the same SCSI target device. The additional SCSI initiator device also has an SNMP agent implementing the SCSI MIB module. In this case, the SCSI target device's MIB module will show that two SCSI initiator devices are attached to it. +-----------+ +----------+ | +----------+ +---------------+ +-+-------+ | | |SCSI |--------------| Virtualization| | SCSI | | |* |Initiator +--------------| Device +-------+ Target | | +--|Device | SCSI | | | Device | *| | | * | | * | | * |--+ | +----------+ Transport +------------+--+ +---------+ | | | | | | | | | | | | | | | | | | | | | | | | | | | | SNMP +-----------+ | SNMP | | +-------+------------------+ SCSI + +-+------------+-------+ | Management| | (NMS) | +-----------+ Figure 3. Multiple Hosts, Virtualization Device and Multiple SCSI Target Devices Figure 3 adds an in-band virtualization device that encapsulates, and possibly modifies, the SCSI target devices' representation to the SCSI Initiator devices. It is common practice for an in-band virtualization device to include both SCSI target and initiator device functionality. Therefore, its SCSI MIB module implementation includes both the SCSI Target device and Initiator device objects. It should be noted that the Virtualization device might implement additional proprietary MIB modules, as the SCSI MIB module does not distinguish between physical and virtual SCSI entities.3.4. Bridging and Virtualization
Storage virtualization is a concept that abstracts storage resources in such a way that, storage entities are provided as pool of logical entities. Usually, the virtualization process is transparent to the storage users (i.e., hosts). Virtualization normally affects the SCSI entities represented to SCSI initiator devices. However, the SCSI MIB module enables the representation of SCSI entities and their respective status, including error and performance-monitoring
statistics. It should be possible to perform a limited number of configuration modification and diagnostic actions. The SCSI entities embodied in the bridging and virtualization devices can be represented by the SCSI MIB module. However, the configuration of bridging and virtualization devices is beyond the above-described scope and therefore should be provided through other MIB modules.3.5. SCSI Command MIB Module
The management of SCSI commands is beyond the scope of this MIB module. Future SCSI Command MIB module can link to this MIB module, through the use of Object Identifiers (OIDs) or INDEX values of appropriate tables.4. Structure of the MIB
This MIB module contains fourteen conformance groups:4.1. The SCSI Device Group
The scsiDeviceGroup group contains the objects general to each SCSI instance: instance, device, and port objects. It contains also the objects referring to the transport(s) used by those SCSI instances. This group is mandatory for all SCSI managed system. Alias objects are provided for SCSI instances and SCSI devices to enable administrators to identify them. These objects contain human-readable administrative text strings, and hence use the SnmpAdminString textual convention from [RFC3411].4.2. The Initiator Group
The scsiInitiatorDeviceGroup contains all the managed information related to a local SCSI initiator device and port. In addition, it contains the managed objects referring to the monitored attached SCSI target devices. Any managed system acting as a SCSI initiator or target/initiator device and port MUST support this group.4.3. The Target Group
The scsiTargetDeviceGroup contains all the managed objects related to a local SCSI target device, a local SCSI target port, monitored attached initiator ports, logical units, and logical unit identifiers.
Managed systems acting as a SCSI target or target/initiator device and port must support this group.4.4. The Discovery Group
The scsiDiscoveryGroup group is a collection of managed objects referring to remote SCSI target devices, remote SCSI target ports, remote logical units, and remote logical unit identifiers discovered by or configured to a managed system acting as a SCSI initiator device. Managed systems acting as a SCSI initiator device and port and supporting remote SCSI target devices or ports configuration or discovery should implement this group.4.5. The LUN Map Group
The scsiLunMapGroup group is a collection of managed objects allowing mapping between SCSI target devices, logical units, and logical unit numbers in one side to remote authorized SCSI initiator devices or ports in another side. Managed systems supporting this mapping should implement the scsiLunMapGroup.4.6. The Target Statistic Group
The scsiTargetDevStatsGroup group is a collection of managed objects representing various statistics referring to a SCSI target device or port. Managed systems acting as a SCSI target device and port supporting statistics should implement this group.4.7. The Target High Speed Statistic Group
The scsiTargetDevHSStatsGroup group is a collection of managed objects representing various statistics referring to a SCSI target device or port. It provides support for systems that can quickly generate countable information because they run at high speed. Managed systems acting as a SCSI target device and port and running at high speed supporting should implement this group.4.8. The LUN Map Statistics Group
The scsiLunMapStatsGroup group is a collection of managed objects representing various statistics referring to remote authorized SCSI initiator devices or ports.
Managed systems acting as a SCSI target device and port and able to gather statistics on remote SCSI initiator devices or ports should implement this group.4.9. The LUN Map Statistics High Speed Group
The scsiLunMapHSStatsGroup group is a collection of managed objects representing various statistics referring to remote authorized SSCI initiator devices or ports. It provides support for systems that can quickly generate countable information because they run at high speed. Managed systems acting as a SCSI target device and port and able to gather statistics on remote SCSI initiator devices or ports and running at high speed should implement this group.4.10. The Initiator Statistics Group
The scsiInitiatorDevStatsGroup group is a collection of managed objects representing various statistics referring to a SCSI initiator device or port. Managed systems acting as a SCSI initiator device and port supporting statistics should implement this group.4.11. The Initiator High Speed Statistic Group
The scsiInitiatorDevHSStatsGroup group is a collection of managed objects representing various statistics referring to a SCSI initiator device or port. It provides support for systems that can quickly generate countable information because they run at high speed. Managed systems acting as a SCSI initiator device and port and running at high speed supporting should implement this group.4.12. The Discovery Statistics Group
The scsiDiscoveryStatsGroup group is a collection of managed objects representing various statistics referring to remote discovered or configured SCSI target devices or ports. Managed systems acting as a SCSI initiator device and port and able to gather statistics on remote SCSI target devices or ports should implement this group.
4.13. The Discovery Statistics High Speed Group
The scsiDiscoveryHSStatsGroup group is a collection of managed objects representing various statistics referring to remote discovered or configured SCSI target devices or ports. It provides support for systems that can quickly generate countable information because they run at high speed. Managed systems acting as a SCSI initiator device and port and able to gather statistics on remote SCSI target devices or ports and running at high speed should implement this group.4.14. The Device Statistics Group
The scsiDeviceStatGroup group is a collection of managed objects representing various statistics referring to a SCSI device. Managed systems able to gather device statistics should implement this group.5. Relationships in This MIB
This section outlines the functionality and the dependency between the MIB tables providing the required management functionality for SCSI initiator and target devices. For specific usage of these tables, the reader should refer to the description of the tables and their respective table entries and attributes. Following is a list of required SCSI initiator-related features, and the respective tables facilitating this functionality: o List all the SCSI initiator ports that should be managed through this MIB module. The table scsiIntrPortTable maintains all the SCSI initiator ports for the SCSI initiator devices in the MIB module. o Provide a list of all SCSI target ports or SCSI target devices to which a SCSI initiator port can attach. This should prevent a SCSI initiator device or port from attaching to SCSI target devices that should be either invisible or inaccessible to it. The entries in this list can be created either manually or by automatic discovery mechanisms (e.g., SLP, iSNS). The ScsiDscTgtTable provides this information. The entries in this table point to the SCSI initiator port, and indicate that the SCSI initiator port can only attach to SCSI target ports or SCSI target devices provided in the respective entries of the ScsiDscTgtTable.
This MIB module permits, but does not require, this table to be
written via SNMP. There are significant security considerations
in allowing writes to this table; see Section 11.
o The information, for the aforementioned SCSI target ports or SCSI
target devices, about the LUs and their respective LUN Ids should
be provided. The scsiDscLunTable and scsiDscLunIdTable maintain
this information.
o The scsiAttTgtPortTable provides the information about the SCSI
target ports each SCSI initiator port is currently communicating
with. This table should be dynamically updated to reflect those
connections.
Following is a list of required SCSI target device-related features,
and the respective tables facilitating this functionality:
o List all the SCSI target ports that should be managed through this
MIB module. The table scsiTgtPortTable maintains all the SCSI
target ports for the SCSI target devices in the MIB module.
o Provide a list of valid SCSI initiator ports or SCSI initiator
devices authorized to attach to a SCSI target port. This list
should feature the concept of "access lists", which are common in
IP routers and switches. The ScsiAuthorizedIntr table provides
this information. This MIB module permits, but does not require
this table to be written via SNMP. There are significant security
considerations in allowing writes to this table; see Section 11.
o It should be possible to specify the list of LUNs exposed to each
SCSI initiator port or device, when it is attached to the SCSI
target device. SCSI target devices must provide a default list of
LUNs. This list of LUNs can either be a unique list for each SCSI
initiator device or be the default list. For each entry in the
ScsiAuthorizedIntr table, a pointer, named
scsiAuthIntrLunMapIndex, indexing the ScsiLunMapTable facilitates
this feature.
o Provide means to monitor all the SCSI initiator ports currently
attached to this SCSI target port. The scsiAttIntrPortTable
provides this information. This table should be dynamically
updated to reflect those connections.
6. Relationship to Other MIBs
6.1. Host Resource MIB
The SCSI MIB module extends objects defined in the host resource MIB module to SCSI-specific entities but does not contain information on software modules such as device drivers. If MIB objects are required for installed packages of SCSI software, then the hrSWInstalledGroup of the Host Resources MIB [RFC2790] are the standard MIB objects to use.6.2. iSCSI MIB Module
The SCSI MIB module defines managed objects for the SCSI protocol layer. The SCSI layer can run on top of several transport layers; iSCSI is one of them. The ISCSI-MIB [ISCSI] is the MIB portion defining the managed objects for the transport called iSCSI. In the same way, a fibre channel or parallel SCSI MIB module would define managed objects for a transport called, respectively, fibre channel or parallel SCSI. The relationship between the SCSI MIB module and any valid transport MIB module is determined via the SCSI port managed table that has an object pointing to the corresponding row, if any, of the relevant table in a transport MIB module.7. Miscellaneous Details
7.1. Names and Identifiers
The names and the identifiers of the SCSI devices, ports, and logical units depend on the underlying transport protocols; their format and length vary accordingly. Please refer to SAM-2 [SAM2] for more details.7.2. Logical Unit Number
The Logical Unit Number is a 64-bit integer. This type does not exist in SMI and therefore, this MIB contains a textual convention defining LUN as an OCTET STRING.7.3. Notifications
Separate SNMP notifications may be enabled/disabled to notify of a change in any of the SCSI device status variables. A notification will be generated theoretically for each occurrence (see restriction
below) of the abnormal status (e.g., if the SCSI device's current status is abnormal and another logical unit changes its status from available to abnormal another notification will occur). To avoid sending an excessive number of notifications due to multiple errors counted, an SNMP agent implementing the SCSI MIB module should not send more than three SCSI notifications in any 10-second period. The 3-in-10 rule was chosen because one notification every three seconds was deemed often enough, but if and when two or three different notifications happen at the same time, it would not be desirable to suppress them. Three notifications in 10 seconds is a happy medium, where a short burst of notifications is allowed, without inundating the network and/or destination host with a large number of notifications. The ultimate control on sending of notifications is in command of the notification generator module specified in [RFC3413].7.4. SCSI Domains
SAM-2 [SAM2] specifies that devices belong to a domain. However, it is not usually possible to determine this from within a system, so domains are not represented within this MIB module.7.5. Counters: 32 Bits and 64 Bits
Some counters, in (newer) high-performance systems, can increase at a fast enough rate such that their representation as Counter32s can cause them to "wrap" in less than an hour. The SMIv2 provides Counter64 as the syntax for such counters. However, (older) SNMPv1 implementations cannot support Counter64s. Thus, this MIB module defines such counters as both Counter32s and Counter64's. The counters in this MIB module that count data are defined in terms of megabytes (i.e., as the number of megabytes of data), such that Counter64s are not required. However, the counters in this MIB module that count commands, when in use at 5 GBit/second with 512-byte read/write operations, could wrap within an hour. Therefore, each of these counters will be defined as both a Counter32 and a Counter64, with the latter being mandatory, for system speeds of 4 Gbit/second or higher. A possible (but not required) implementation strategy is to have the value of each Counter32 be the same value as the low-order 32 bits of the corresponding Counter64.
7.6. Local versus Remote Entities
This MIB module qualifies often SCSI entities as local or remote. The local entities are the ones for which the agent is reporting. The remote entities are the ones that the local entities are in communication with via the SCSI protocol.8. Abbreviations
This MIB module will use the following abbreviations: Inst = Instance Dev = SCSI Device Tgt = SCSI Target Device Intr = SCSI Initiator Device Att = Attached Id = Identifier Dsc = Discovered pSCSI = Parallel SCSI
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