9 Setting Up a Shared Tape Service

An available server environment (ASE) tape service depends on a set of one or more tape devices. It may also include media changer devices and file systems. A tape service enables the system administrator to configure the POLYCENTER NetWorker server and the servers for other client/server-based applications, for failover. The tape drive(s), media changer(s), and file systems all fail over as a unit.

Eligible servers must be written to react appropriately to certain events on the shared SCSI bus, such as bus and bus device resets. Bus and device resets cause any tape device on the shared SCSI bus to rewind. Therefore, a tape server application will inspect the errno value and extended error information returned from its I/O call and reposition the tape. Note that because the commonly used utilities tar, cpio, dump, and vdump are not designed in this way, they may unexpectedly terminate when used within an ASE, due to a node state transition or other normal ASE event.

This chapter describes how to use the asemgr to add a tape service to an ASE. It describes the components of the service and includes an example of setting up and modifying a tape service.

9.1 Tape Service Requirements

Tape services have the following requirements:

A tape service that has an Internet Protocol (IP) name must be included in the /etc/hosts file on each member system before you set up the tape service.

Service names and member system names must be unique; you cannot use a name for the tape service that is the same as a system name.

A tape service IP name must adhere to the conventions for naming a system, as described in the DIGITAL UNIX Installation Guide.

A tape service IP name can be associated with any subnet directly connected to all the member systems. If you are using a distributed database lookup service, such as the Network Information Service (NIS), be sure that the service name information is local to all the member systems by making all the member systems either master or slave servers, or by specifying the service name information in the local /etc/hosts file. Ensure that the /etc/svc.conf file specifies local as the first entry.

In addition to these requirements, consider adjusting the timeouts used by the tape driver. Some tape motion operations, such as rewinds, forward and backward spacing files and records, and writing file marks, may cause the tape driver to time out for long periods of time. As a result, certain failures that would trigger a service relocation may not be detected until the timeout expired. To avoid this problem, the administrator can set the timeouts used by the tape driver for particular tape device models in the/etc/ddr.dbase file.

When adjusting tape driver settings, ensure that raw tape devices are consistently named. See the DIGITAL UNIX Installation Guide for recommendations on creating consistent device special files for ASE shared tape service.

To adjust the timeouts used by a tape driver, follow these steps:

Modify the device type entries in the /etc/ddr.dbasefile.

After making these changes to the /etc/ddr.dbasefile, run ddr_config -c to make the changes take effect without a reboot. These settings will be picked up automatically on future reboots.

The following example shows sample entries in the /etc/ddr.dbase file. These changes would set the timeout values to 300 seconds (5 minutes). These settings should be placed after the PARAMETERS section of the particular tape entry you want to modify.

SCSIDEVICE
    #
    Type = tape
    Name = "DEC" "TZ30"
    #
    PARAMETERS:
        TypeSubClass        = tk
        MaxTransferSize     = 64512
        SyncTransfers       = disabled
        TagQueueDepth       = 0
        ReadyTimeSeconds    = 45                # seconds
 
    # Use "default" tape densities
 
    ATTRIBUTE:
        AttributeName = "BDRatBoot"
        Length        = 1
        ubyte[0]      = 1
 
    ATTRIBUTE:
        AttributeName = "REW_TIMEOUT"
        Length        = 8
        ubyte[0]      = 300
 
    ATTRIBUTE:
        AttributeName = "LOAD_TIMEOUT"
        Length        = 8
        ubyte[0]      = 300
 
 
    ATTRIBUTE:
        AttributeName = "SPACE_TIMEOUT"
        Length        = 8
        ubyte[0]      = 300
 
    ATTRIBUTE:
        AttributeName = "SEOD_TIMEOUT"
        Length        = 8
        ubyte[0]      = 300

9.2 Tape Service Components

When you add a tape service, you can specify the following information:

Service name--Must be unique and cannot contain a slash (/). Optionally, you can specify a tape service name that is also an IP host name. The IP host name must be specified in each member system's /etc/hosts file. See hosts(4) for more information. Service names that are IP host names must adhere to the conventions for naming a system, as described in the DIGITAL UNIX Installation Guide.

Tape Information-- One or more character device special files to define the tape storage for this service.

Media Changer-- Character device special files to define the media changer(s) for this service (if applicable).

Disk Information-- One or more device special files, Advanced File System (AdvFS) filesets, or Logical Storage Manager (LSM) volumes to define the disk storage for this service.

Automatic Placement Policy (ASP)-- Select the policy you want ASE to use when choosing a member to run this service: Balanced Service Distribution, Favor Members, or Restrict to Favored Members. See Chapter 4 for information about the ASP policies.

User-defined action scripts-- Add any action scripts necessary to fail over the application. See Chapter 4 for information about creating action scripts.

9.3 Adding a Tape Service

Example 9-1 shows how to add a tape service. No media changer is considered in this example. The tape service will be modified in Example 9-2 to include a media changer.

Example 9-1: Adding a Tape Service

# asemgr

.
.
.
Adding a service
 
Select the type of service:
 
    1)  NFS service
    2)  Disk service
    3)  User-defined service
    4)  DRD service
    5)  Tape service
 
    q)  Quit without adding a service   
    x)  Exit                             ?)  Help
 
Enter your choice [1]: 5
 
You are now adding a new tape service to your ASE.  
 
A tape service consists of one or more tape devices, zero or more media
changer devices, and an optional disk configuration that are failed over
together. The disk configuration can include UFS filesystems, AdvFS
filesets, LSM volumes, or raw disk information.
 
                     Tape Service Name
 
The name of a tape service must be a unique service name within this ASE.
Optionally, an IP address may be assigned to a tape service.  In this
case, the name must be a unique IP host name set up for this service and
present in the local hosts database on all ASE members.
 
Enter the tape service name ('q' to quit): sh-tape01
 
Assign an IP address to this service? (y/n): n
 
                     Specifying Tape Information
 
Enter one or more character device special files to define the tape storage
for this service.
 
    For example:	Rewind on close, high density:	     /dev/rmt0h
			No rewind on close, medium density:  /dev/nrmt1m
 
To end the list, press the Return key at the prompt.  To quit, enter 'q'.
 
Enter a tape special file name (press 'Return' to end): /dev/rmt0h
 
Enter a tape special file name (press 'Return' to end): [Return] 
 
                     Specifying Media Changer Information
 
Enter zero or more character device special files to define the media changers
for this service.
 
    For example:	/dev/mc16
 
To end the list, press the Return key at the prompt.  To quit, enter 'q'.
 
Enter a media changer special file name (press 'Return' to end): [Return] 
 
                     Specifying Disk Information
 
Enter one or more device special files, AdvFS filesets, or LSM volumes 
to define the disk storage for this service.
 
    For example:	Device special file:      /dev/rz3c
			AdvFS fileset:            domain1#set1
			LSM volume:               /dev/vol/dg1/vol01
 
To end the list, press the Return key at the prompt.
 
Enter a device special file, an AdvFS fileset, or an LSM volume as storage
for this service (press 'Return' to end): /dev/rrz9c
 
                  Mount Point
 
The mount point is the directory on which to mount `/dev/rz9c`.
If you do not want it mounted, enter "NONE".
 
Enter the mount point or NONE: NONE
 
                     Specifying Disk Information
 
Enter one or more device special files, AdvFS filesets, or LSM volumes 
to define the disk storage for this service.
 
    For example:	Device special file:      /dev/rz3c
			AdvFS fileset:            domain1#set1
			LSM volume:               /dev/vol/dg1/vol01
 
To end the list, press the Return key at the prompt.
 
Enter a device special file, an AdvFS fileset, or an LSM volume as storage
for this service (press 'Return' to end): [Return] 
 
 
Modifying user-defined scripts for `sh-tape01`:
 
    1)  Start action
    2)  Stop action
    3)  Add action
    4)  Delete action
 
    x)  Exit - done with changes
 
Enter your choice [x]: [Return] 
 
	Selecting an Automatic Service Placement (ASP) Policy
 
Select the policy you want ASE to use when choosing a member
to run this service:
 
    b)  Balanced Service Distribution
    f)  Favor Members
    r)  Restrict to Favored Members
 
                                         ?)  Help
 
Enter your choice [b]: b
 
 
	Selecting an Automatic Service Placement (ASP) Policy
 
Do you want ASE to consider relocating this service to another member
if one becomes available while this service is running (y/n/?): n
 
Enter 'y' to add Service 'sh-tape01' (y/n): y
Adding service...
Starting service...
Service sh-tape01 successfully added...
#

In Example 9-2 the tape service sh-tape01 will be modified to add a media changer. The tape drive, media changer, and disk will all be failed over as a unit.

Example 9-2: Modifying a Tape Service

# asemgr

.
.
.
	
		Service Configuration
 
    a)  Add a new service
    m)  Modify a service
    o)  Modify a service without interrupting its availability
    d)  Delete a service
    s)  Display the status of a service
    c)  Display the configuration of a service
 
    q)  Quit (back to Managing ASE Services)
    x)  Exit                             ?)  Help
 
Enter your choice [q]: m 
 
	Modifying a Service
 
Select the service you want to modify:
 
    1)  tiebreaker1 on rtcr3b
    2)  sh-tape01 on rtcr4b
 
    q)  Quit without modifying a service
    x)  Exit                             ?)  Help
 
Enter your choice [q]: 2
 
Select what you want to modify in service `sh-tape01`:
 
    g)  General service information
    a)  Automatic service placement (ASP) policy
 
    q)  Quit without modifications      
    x)  Exit                             ?)  Help
 
Enter your choice [g]: g
 
                Tape Service Modification
 
The following menu lists the storage configuration for the tape service 
`sh-tape01`.
 
You can modify the following storage configuration, add more storage, or 
perform miscellaneous modifications.
 
Select what to modify in tape service `sh-tape01`:
 
 
    1)  /dev/rmt0h	(tape device)	
    a)  Add a tape device, media changer, UFS file system, Advfs fileset,
        LSM volume, or raw disk
    m)  Miscellaneous modifications for `sh-tape01`
    q)  Quit without making any changes
    x)  Exit (done with modifications)
 
 
Enter your choice [x]: a
 
                     Specifying Tape Information
 
Enter one or more character device special files to define the tape storage
for this service.
 
    For example:	Rewind on close, high density:	     /dev/rmt0h
			No rewind on close, medium density:  /dev/nrmt1m
 
To end the list, press the Return key at the prompt.  To quit, enter 'q'.
 
Enter a tape special file name (press 'Return' to end): [Return] 
 
                     Specifying Media Changer Information
 
Enter zero or more character device special files to define the media changers
for this service.
 
    For example:	/dev/mc16
 
To end the list, press the Return key at the prompt.  To quit, enter 'q'.
 
Enter a media changer special file name (press 'Return' to end): /dev/mc20b 
 
Enter a media changer special file name (press 'Return' to end): [Return] 
 
                     Specifying Disk Information
 
Enter one or more device special files, AdvFS filesets, or LSM volumes 
to define the disk storage for this service.
 
    For example:	Device special file:      /dev/rz3c
			AdvFS fileset:            domain1#set1
			LSM volume:               /dev/vol/dg1/vol01
 
To end the list, press the Return key at the prompt.
 
Enter a device special file, an AdvFS fileset, or an LSM volume as storage
for this service (press 'Return' to end):  [Return]
 
Select what to modify in tape service `sh-tape01`:
 
 
    1)  /dev/rmt0h	(tape device)	 
    2)  /dev/mc20b	(media changer)	
    a)  Add a tape device, media changer, UFS file system, Advfs fileset,
        LSM volume, or raw disk
    m)  Miscellaneous modifications for `sh-tape01`
    q)  Quit without making any changes
    x)  Exit (done with modifications)
Enter your choice [x]: x
 
NOTE: Modifying a service causes it to stop and then restart.  If you do
not want to interrupt the service availability, do not modify the service.
 
Enter 'y' to modify service 'sh-tape01' (y/n): y
Stopping service...
Deleting service...
Adding service...
Starting service...
Service successfully updated.
#