Document revision date: 30 March 2001

With the introduction of multipath SCSI support, as described in Chapter 6, it is necessary to identify specific paths from the host to the storage subsystem. This is done by concatenating the SCSI pseudodevice name, a decimal point (.), and the WWID of the storage subsystem port that is being accessed. For example, the Fibre Channel path shown in Figure 7-12 is named PGB0.4000-1FE1-0000-0D04.

Refer to Chapter 6 for more information on the display and use of the Fibre Channel path name.

7.4.2.3 Fibre Channel Disk Device Identification

The four identifiers associated with each FC disk device are shown in Figure 7-13.

Figure 7-13 Fibre Channel Disk Device Naming

The logical unit number (LUN) is used by the system as the address of a specific device within the storage subsystem. This number is set and displayed from the HSG console by the system manager. It can also be displayed by the OpenVMS SDA utility.

Each Fibre Channel disk device also has a WWID to provide permanent, unique identification of the device. The HSG device WWID is 128 bits. Half of this identifier is the WWID of the HSG that created the logical storage device, and the other half is specific to the logical device. The device WWID is displayed by the HSG console and the AlphaServer console.

The third identifier associated with the storage device is a user-assigned device identifier. A device identifier has the following attributes:

• User assigned at the HSG console.
• User must ensure it is cluster unique.
• Moves with the device.
• Can be any decimal number from 0 to 32766, except for MSCP served devices.
  If the FC disk device is MSCP served, the device identifier is limited to 9999. This restriction will be removed in a future release.

The device identifier has a value of 567 in Figure 7-13. This value is used by OpenVMS to form the device name so it must be unique throughout the cluster. (It may be convenient to set the device identifier to the same value as the logical unit number (LUN). This is permitted as long as the device identifier is unique throughout the cluster.)

A Fibre Channel storage device name is formed by the operating system from the constant $1$DGA and a device identifier, nnnnn . The only variable part of the name is its device identifier, which you assign at the HSG console. Figure 7-13 shows a storage device that is known to the host as $1$DGA567 .

7.5 Fibre Channel Tape Support (Alpha)

This section describes the configuration requirements and user commands necessary to utilize the Fibre Channel tape functionality. Fibre Channel tape functionality refers to the support of SCSI tapes and SCSI tape libraries in an OpenVMS Cluster system with shared Fibre Channel storage. The SCSI tapes and libraries are connected to the Fibre Channel by a Fibre-to-SCSI bridge known as the Modular Data Router (MDR).

7.5.1 Minimum Hardware Configuration

Following is the minimum Fibre Channel tape hardware configuration:

• Alpha system with KGPSA adapter
• Compaq Modular Data Router (MDR), minimum firmware revision 1170
• Fibre Channel Switch
• Tape library, for example:
  • ESL9000 series
  • TL891
  • TL895
• Individual tapes, for example:
  • TZ89
  • DLT8000

This section provides detailed background information about Fibre Channel Tape device naming.

Tape and medium changer devices are automatically named and configured using the SYSMAN IO FIND and IO AUTOCONFIGURE commands described in Section 7.5.3. System managers who configure tapes on Fibre Channel should refer directly to this section for the tape configuration procedure.

7.5.2.1 Tape and Medium Changer Device Names

Fibre Channel tapes and medium changers are named using a scheme similar to Fibre Channel disk naming.

On parallel SCSI, the device name of a directly attached tape implies the physical location of the device; for example, MKB301 resides on bus B, SCSI target ID 3, and LUN 1. Such a naming scheme does not scale well for Fibre Channel configurations, in which the number of targets or nodes can be very large.

Fibre Channel tape names are in the form $2$MGAn. The letter for the controller is always A, and the prefix is $2$. The device mnemonic is MG for tapes and GG for medium changers. The device unit n is automatically generated by OpenVMS.

The name creation algorithm chooses the first free unit number, starting with zero. The first tape discovered on the Fibre Channel is named $2$MGA0, the next is named $2$MGA1, and so forth. Similarly, the first medium changer detected on the Fibre Channel is named $2$GGA0. The naming of tapes and medium changers on parallel SCSI buses remains the same.

Note the use of allocation class 2. Allocation class 1 is already used by devices whose name is keyed by a user-defined identifier (UDID), as with HSG Fibre Channel disks ($1$DGAnnnn) and HSG console command LUNs ($1$GGAnnnn).

An allocation class of 2 is used by devices whose names are obtained from the file, SYS$DEVICES.DAT. The names are based on a worldwide identifier (WWID) key, as described in the following sections. Also note that, while GG is the same mnemonic used for both medium changers and HSG Command Console LUNs (CCLs), medium changers always have an allocation class of 2 and HSG CCLs an allocation class of 1.

Tape and medium changer names are automatically kept consistent within a single OpenVMS Cluster system. Once a tape device is named by any node in the cluster, all other nodes in the cluster automatically choose the same name for that device, even if this overrides the first free unit number algorithm. The chosen device name remains the same through all subsequent reboot operations in the cluster.

If multiple nonclustered Alpha systems exist on a SAN and need to access the same tape device on the Fibre Channel, then the upper-level application must provide consistent naming and synchronized access.

7.5.2.2 Use of Worldwide Identifiers (WWIDs)

For each Fibre Channel tape device name, OpenVMS must uniquely identify the physical device that is associated with that name.

In parallel SCSI, directly attached devices are uniquely identified by their physical path (port/target/LUN). Fibre Channel disks are uniquely identified by user-defined identifiers (UDIDs). These strategies are either unscalable or unavailable for Fibre Channel tapes and medium changers.

Therefore, the identifier for a given Fibre Channel tape or medium changer device is its worldwide identifier (WWID). The WWID resides in the device firmware and is required to be unique by the Fibre Channel standards.

WWIDs can take several forms, for example:

• IEEE registered WWID (64-bit binary)
• Vendor ID plus product ID plus serial number (ASCII)

The overall WWID consists of the WWID data prefixed by a binary WWID header, which is a longword describing the length and type of WWID data.

In general, if a device reports an IEEE WWID, OpenVMS chooses this as the unique identifying WWID for the device. If the device does not report such a WWID, then the ASCII WWID is used. If the device reports neither an IEEE WWID nor serial number information, then OpenVMS does not configure the device. During the device discovery process, OpenVMS rejects the device with the following message:

%SYSMAN-E-NOWWID, error for device Product-ID, no valid WWID found.

The WWID structures can be a mix of binary and ASCII data. These formats are displayable and are intended to be consistent with those defined by the console WWIDMGR utility. Refer to the WWIDMGR User's Manual for additional information. Note that if the data following the WWID header is pure ASCII data, it must be enclosed in double quotation marks.

The displayable format of a 64-bit IEEE WWID consists of an 8-digit hexadecimal number in ASCII (the WWID header), followed by a colon (:) and then the IEEE WWID data. For example:

0C000008:0800-4606-8010-CD3C

The displayable format of an ASCII WWID consists of an 8-digit WWID header, followed by a colon (:) and then the concatenation of the 8-byte vendor ID plus the 16-byte product ID plus the serial number. For example:

04100022:"COMPAQ DLT8000 JF71209240"

Fibre Channel tape and medium changer devices are configured according to information found in the SYS$SYSTEM:SYS$DEVICES.DAT file. This is an ASCII file consisting of two consecutive records per device, where the two records are in the following form:

[Device $2$devnam] WWID = displayable_identifier

During autoconfiguration, the Fibre Channel is probed and the WWIDs are fetched for all devices. If the fetched WWID matches an entry in the memory-resident copy of the SYS$DEVICES.DAT file, then the device is configured using the device name that has been paired with that WWID.

As an example, the following portion of SYS$DEVICES.DAT causes the eventual configuration of devices named $2$MGA300 and $2$MGA23:

! [Device $2$MGA300] WWID = 04100022:"COMPAQ DLT8000 JF71209240" ! [Device $2$mga23] WWID = 04100022:"DEC TZ89 (C) DECJL01164302"

Although the file is typically read and written only by OpenVMS utilities, in rare instances you may need to edit the file. In OpenVMS Alpha Version 7.3, you can change only the unit number of the device, as described in Section 7.5.5. The internal syntax rules governing the file are summarized as follows:

• Comment lines (beginning with !) and blank lines are permitted.
• Any white space (or none) can separate [Device from the device name represented by $2$xxx ].
• Failure to supply the $2$ prefix will result in a console warning.

Similarly, on the line containing WWID = , any white space (or none) can appear on either side of the equals sign. All lines must be left-justified, and all lines must be less than 512 characters.

The parsing of this file is not case sensitive, with one important exception: all characters enclosed within double quotation marks are taken literally, so that characters such as spaces and lowercase letters are significant. In the case of ASCII data enclosed by double quotation marks, there must be no space between the colon and the double quotation mark.

Also, if more than one WWID = line follows a single [Device devnam] line, the last WWID = value takes precedence. Normally, however, there is exactly one WWID = line per [Device devnam] line.

Similarly, if two or more [Device devnam] lines specify the same device name but different WWIDs, only the last device name and WWID specified in the file is used.

This file is read at boot time, and it is also read from and written to by the SYSMAN IO FIND_WWID command. If there are additional system-specific copies of the SYS$DEVICES.DAT file, their tape naming records become automatically compatible as a result of running SYSMAN IO FIND_WWID on each system. The SYSMAN IO FIND_WWID command is described in more detail in the following section.

7.5.3 New Commands and Features for Fibre Channel Tape Devices

Two new System Management utility (SYSMAN) commands have been added. They are:

• IO FIND_WWID
  Probes all ports on the Fibre Channel and detects all previously undiscovered tapes and medium changers, and assigns a name to each. Displays a list of the devices and their assigned device names, and automatically records this information in the SYS$SYSTEM:SYS$DEVICES.DAT file. Also updates relevant local and clusterwide memory structures.
  Use this command prior to running the SYSMAN command IO AUTOCONFIGURE.
  Requires the CMKRNL privilege.
• IO REPLACE_WWID
  Updates appropriate file and memory data structures in case one tape drive must be physically replaced by another tape drive at the same FC LUN location.
  Requires the CMKRNL privilege.

The following DCL enhancements have been made:

• The SHOW DEVICE/FULL command now displays the WWID for Fibre Channel tape devices.
• The F$GETDVI lexical function now supports the new keyword WWID , which returns the Fibre Channel tape device's WWID.

This section lists the steps required to configure a new tape or medium changer on the Fibre Channel.

7.5.4.1 Basic Configuration Steps: Summary

The basic steps for configuring new Fibre Channel tape devices in a cluster are as follows:

1. Power on the new tape device(s).
2. Powercycle the MDR to update MDR mapping information.
3. Run SYSMAN to assign device names and configure the devices:

   $ MC SYSMAN SYSMAN> SET ENVIRONMENT/CLUSTER ! Execute on all nodes SYSMAN> IO FIND_WWID ! Assign names SYSMAN> IO AUTOCONFIGURE/LOG ! Configure devices SYSMAN> EXIT

You need to perform these steps only once for the initial configuration. After any subsequent system reboot, the devices will appear automatically.

7.5.4.2 Basic Configuration Steps: Details

Prior to configuring a tape device on Fibre Channel, the worldwide identifier (WWID) of the device must be detected and stored, along with a device name, in the text file SYS$SYSTEM:SYS$DEVICES.DAT. This is accomplished by using the new SYSMAN command IO FIND_WWID.

The IO FIND_WWID command probes all ports on the Fibre Channel and locates all tape and medium changer devices connected to an MDR. For tapes and medium changers that have not been detected by a previous IO FIND_WWID command, IO FIND_WWID assigns a device name, retrieves the WWID of the device, stores the device name and WWID data in the SYS$SYSTEM:SYS$DEVICES.DAT file, and updates memory structures.

Since the primary goal of IO FIND_WWID is to populate the SYS$DEVICES.DAT file, you need to invoke the IO FIND_WWID command only once for each device. IO FIND_WWID does not configure the $2$MGAnnnn: device for use by an application.

Once the information is stored in the file, subsequent use of the IO AUTOCONFIGURE command reads a memory-resident copy of the file and configures the tape and medium changer devices automatically, loading or connecting the device drivers as needed. The SYS$DEVICES.DAT file is read into memory during each system reboot; this action initiates the automatic configuration of tapes and medium changers on the Fibre Channel.

Note that running the IO FIND_WWID command for the first time detects all existing tape and medium changer devices on the system. If you add additional Fibre Channel tape devices to the system at a later time, you must first powercycle the MDR to update internal mapping information, and then run the IO FIND_WWID command again to append the new device information to the SYS$DEVICES.DAT file.

In an OpenVMS Cluster environment, various data structures in memory must be updated on each system when a new Fibre Channel tape device is added. To accomplish this, Compaq recommends that you run the SYSMAN IO FIND_WWID command on each Alpha node in the cluster. Alternatively, you can run IO FIND_WWID on one node, and then reboot the other nodes that share that same system disk, because the SYS$DEVICES.DAT file is read at boot time and causes memory structures to be correctly initialized.

In the case of multiple system disks in the cluster, ensure that all copies of the SYS$DEVICES.DAT file are kept consistent, preferably by running the IO FIND_WWID command on all nodes. Alternatively, you can run IO FIND_WWID to update just one SYS$DEVICES.DAT file, and then manually edit the remaining SYS$DEVICES.DAT files by cutting and pasting the appropriate device name and WWID records from the original file to the target files.

Compaq recommends that you refrain from copying the entire original file to another system disk. The SYS$DEVICES.DAT file is also used to define port allocation classes (PACs), and PAC entries could be transferred inadvertently to the target system.

Following is a configuration example using a TL891 tape library on a single node.

First, the SYSMAN command IO FIND_WWID displays a list of all previously undiscovered tape devices and their device names.

$ MCR SYSMAN IO FIND_WWID %SYSMAN-I-OUTPUT, command execution on node SAMPLE On port _SAMPLE$PGA0:, the following tape WWIDs and their proposed device names have been found but not yet configured: [Device $2$GGA0] WWID=04100024:"DEC TL800 (C) DEC3G9CCR82A017" [Device $2$MGA0] WWID=04100022:"DEC TZ89 (C) DECCX939S2777" [Device $2$MGA1] WWID=04100022:"DEC TZ89 (C) DECCX942S6295"

Note that the overall WWID consists of everything to the right of the equals sign. Each such WWID is unique; however, the header portion may not be unique, because the header reflects only the basic type and length of the the WWID data.

The IO FIND_WWID command automatically records the information about the new tape devices in SYS$SYSTEM:SYS$DEVICES.DAT:

$ TYPE SYS$SYSTEM:SYS$DEVICES.DAT ! ! Updated 23-OCT-2000 14:17:41.85: DEC TL800 ! [Device $2$GGA0] WWID=04100024:"DEC TL800 (C) DEC3G9CCR82A017" ! ! ! Updated 23-OCT-2000 14:17:41.93: DEC TZ89 ! [Device $2$MGA0] WWID=04100022:"DEC TZ89 (C) DECCX939S2777" ! ! ! Updated 23-OCT-2000 14:17:42.01: DEC TZ89 ! [Device $2$MGA1] WWID=04100022:"DEC TZ89 (C) DECCX942S6295" !

Next, the SYSMAN command IO AUTOCONFIGURE configures the tape device.

$ MCR SYSMAN IO AUTOCONFIGURE/LOG %SYSMAN-I-OUTPUT, command execution on node SAMPLE %IOGEN-I-PREFIX, searching for ICBM with prefix SYS$ %IOGEN-I-PREFIX, searching for ICBM with prefix DECW$ %IOGEN-I-SCSIPOLL, scanning for devices through SCSI port PKA0 %IOGEN-I-SCSIPOLL, scanning for devices through SCSI port PKB0 %IOGEN-I-FIBREPOLL, scanning for devices through FIBRE port PGA0 %IOGEN-I-CONFIGURED, configured device GGA0 %IOGEN-I-CONFIGURED, configured device MGA0 %IOGEN-I-CONFIGURED, configured device MGA1

Fianlly, the SHOW DEVICE/FULL command displays the WWID of the tape device.

$ SHOW DEVICE/FULL $2$MG Magtape $2$MGA0: (SAMPLE), device type TZ89, is online, file-oriented device, available to cluster, error logging is enabled, controller supports compaction (compaction disabled), device supports fastskip. Error count 0 Operations completed 0 Owner process "" Owner UIC [SYSTEM] Owner process ID 00000000 Dev Prot S:RWPL,O:RWPL,G:R,W Reference count 0 Default buffer size 2048 WWID 04100022:"DEC TZ89 (C) DECCX939S2777" Density default Format Normal-11 Allocation class 2 Volume status: no-unload on dismount, position lost, odd parity. Magtape $2$MGA1: (SAMPLE), device type TZ89, is online, file-oriented device, available to cluster, error logging is enabled, controller supports compaction (compaction disabled), device supports fastskip. Error count 0 Operations completed 0 Owner process "" Owner UIC [SYSTEM] Owner process ID 00000000 Dev Prot S:RWPL,O:RWPL,G:R,W Reference count 0 Default buffer size 2048 WWID 04100022:"DEC TZ89 (C) DECCX942S6295" Density default Format Normal-11 Allocation class 2 Volume status: no-unload on dismount, position lost, odd parity.

The F$GETDVI lexical function also retrieves the displayable WWID:

$ write sys$output f$getdvi("$2$MGA0","WWID") 04100022:"DEC TZ89 (C) DECCX939S2777"

Once the device is named and configured, you can use the device in the same way that you use parallel SCSI tapes with DCL commands such as INITIALIZE, MOUNT, BACKUP, and COPY. Refer to the installation guide for individual tape layered products for details on product-specific support of Fibre Channel tapes.

Note that while medium changers on Fibre Channel are autoconfigured, the medium changers on parallel SCSI continue to require the IO CONNECT command to load the device driver. It is impossible to manually connect a Fibre Channel medium changer by the SYSMAN IO CONNECT command because the device name does not imply the device's physical location, as it does in parallel SCSI.

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