6 Setting Up a Disk Service

A disk service includes one or more file systems, Advanced File System (AdvFS) filesets, or Logical Storage Manager (LSM) volumes that are highly available. Disk services can also include a disk-based application that is highly available. An example of an application that you can use in a disk service is a database application.

You can assign a disk service name its own Internet address. The member system that runs the service responds to this address. This makes the service autonomous and not dependent on the availability of any particular member system. Clients access the service by including the service name and the exported directory path in their /etc/fstab file. If the service stops on a member system, it fails over to a viable system, and clients only experience a short timeout.

If you assign an Internet address to a disk service name, you can use the POLYCENTER NetWorker Save and Restore (NetWorker) to back up the service's storage. NetWorker treats the disk service as an independent client and stores the storage indexes under the name of the service. This enables you to back up and recover the service's storage independent of the member system running the service. See the NetWorker documentation for information about using NetWorker to back up a disk service's storage.

Before you set up a disk service, you must prepare the disks to be used in the service and install any application used in the service. To fail over an application, in addition to disk, at a minimum, you must create a user-defined start action script that includes the commands to start the application, and create a user-defined stop action script that includes the commands to stop the application. See Chapter 4 for more information about preparing disks, applications, and action scripts for a service.

Note that a disk service is not the same as a distributed raw disk (DRD) service. Disk services typically involve file system usage, while DRD services provide access to raw physical disks throughout a Production Server cluster.

6.1 Disk Service Requirements

Disk services have the following requirements:

Disk service names that are also Internet Protocol (IP) names must be included in the local /etc/hosts file on each member system before you set up the disk service.

You cannot use a disk service IP name that is the same as the name of any system. Service names and member system names must be unique.

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

A disk service IP name can be associated with any IP subnet that is 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. To do this, make all the member systems either master or slave servers, or specify the service name information in the local /etc/hosts file. Be sure your /etc/svc.conf file specifies local as the first entry.

Do not manually mount or dismount disks that will be used in a disk service.

To use NetWorker to back up disk service data, you must specify a mount point for each file system, fileset, or volume when you add the service.

If you do not specify a mount point for an Advanced File System (AdvFS) fileset, a member system may panic unless the following conditions are met:
- Before you add the disk service, make sure that the fileset is not already mounted.
- If you mount a fileset in your own user-defined action scripts, make sure that the user-defined stop action script unmounts the fileset and returns an error code if the unmount fails.

6.2 Disk Service Components

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

Service name--A service name must be unique and cannot contain a slash (/). Optionally, you can specify a disk service name that is also an Internet Protocol (IP) host name. The IP host name must be specified in each member system's local /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.

Automatic Service Placement (ASP) policy--See Chapter 4 for information about the ASP policies.

UNIX file systems, AdvFS fileset names, or Logical Storage Manager (LSM) volumes--See Chapter 4 for information about setting up disks.

Mount point for each file system, fileset, or volume--Client systems will specify this mount point in their /etc/fstab files to access the service's file systems. You can specify NONE if you do not want the TruCluster software to automatically mount the file system, fileset, or volume.

Mode (either read/write or read-only) and any mount options other than the default options for each file system, fileset, or volume.

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

6.3 Adding a Basic Disk Service

Example 6-1 shows how to add a disk service that uses an Internet Protocol (IP) name, an Advanced File System (AdvFS) fileset on a Logical Storage Manager (LSM) volume, and pathnames for action scripts to start and stop the service.

Example 6-1: Adding a Disk Service Using Your Own Action Scripts

# 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]: 2
 
You are now adding a new disk service to the ASE.
 
A disk service consists of a disk-based application and disk
configuration that are failed over together.  The disk
configuration can include UFS file systems, AdvFS filesets,
LSM disk groups, or raw disk information.
 
                    Disk Service Name
 
The name of a disk service must be a unique service name. Optionally,
an IP address may be assigned to a disk service.  In this case, the
name must be a unique IP host name set up for this service and
must be in the local hosts database on all the ASE member systems.
 
Enter the disk service name: disk1
 
Assign an IP address to this service? (y/n): y
 
Checking to see if disk1 is a valid host...
 
                  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): domain2#fs1
 
AdvFS domain `domain2` has the following volumes:
     /dev/vol/dg3/vol01
 
Is this correct (y/n) [y]: y
 
Following is a list of device(s) and pubpath(s) for disk group dg3:
 
        DEVICE  PUBPATH
        rz20c   /dev/rz20c
 
Is this correct (y/n) [y]: y
 
                  Mount Point
 
The mount point is the directory on which to mount`domain2#fs1`.
If you do not want it mounted, enter "NONE".
 
Enter the mount point or NONE: /fs1_disk1
 
              AdvFS Fileset Read-Write Access
 
Mount `domain2#fs1` fileset with read-write or read-only access?
 
    1)  Read-write
    2)  Read-only
 
Enter your choice [1]: 2
 
              AdvFS Mount Options Modification
 
Enter a comma-separated list of any mount options you want to use
for `domain2#fs1` fileset (in addition to the defaults listed in
the mount.8 reference page).  If none are specified, only the
default mount options are used.
 
Enter options (Return for none):[Return]
 
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 `disk1`:
 
    1)  Start action
    2)  Stop action
    3)  Add action
    4)  Delete action
 
    x)  Exit - done with changes
 
Enter your choice [x]: 1
 
Modifying the start action script for `disk1`:
 
    a)  Add a start action script
    e)  Edit the start action script
    g)  Modify the start action script arguments []
    t)  Modify the start action script timeout [60]
    r)  Remove the start action script
    x)  Exit - done with changes
 
Enter your choice [x]: a
 
Enter the full pathname of your start action script or "default"
for the default script (x to exit): /usr/sbin/dbase_account
 
Enter the argument list for the start action script (x to exit): start
 
Enter the timeout in seconds for the start action script [60]:[Return]
 
Modifying the start action script for `disk1`:
 
    f)  Replace the start action script
    e)  Edit the start action script
    g)  Modify the start action script arguments [start]
    t)  Modify the start action script timeout [60]
    r)  Remove the start action script
    x)  Exit - done with changes
 
Enter your choice [x]: x
 
Modifying user-defined scripts for `disk1`:
 
    1)  Start action
    2)  Stop action
    3)  Add action
    4)  Delete action
 
    x)  Exit - done with changes
 
Enter your choice [x]: 2
 
Modifying the stop action script for `disk1`:
 
    a)  Add stop action script
    e)  Edit the stop action script
    g)  Modify the stop action script arguments []
    t)  Modify the stop action script timeout [60]
    r)  Remove the stop action script
    x)  Exit - done with changes
 
Enter your choice [x]: a
 
Enter the full pathname of your stop action script or "default"
for the default script (x to exit): /usr/sbin/dbase_account
 
Enter the argument list for the stop action script (x to exit): stop
 
Enter the timeout in seconds for the stop action script [60]:[Return]
 
Modifying the stop action script for `disk1`:
 
    f)  Replace the stop action script
    e)  Edit the stop action script
    g)  Modify the stop action script arguments [stop]
    t)  Modify the stop action script timeout [60]
    r)  Remove the stop action script
    x)  Exit - done with changes
 
Enter your choice [x]: [Return]
 
Modifying user-defined scripts for `disk1`:
 
    1)  Start action
    2)  Stop action
    3)  Add action
    4)  Delete action
    x)  Exit - done with changes
 
Enter your choice [x]: x
 
    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
    x)  Exit to service config menu      ?)  Help
 
Enter your choice [b]: r
 
        Selecting an Automatic Service Placement (ASP) Policy
 
Select the favored member(s) IN ORDER for service 'disk1':
 
    1)  gideon
    2)  toto
    x)  No favored members               ?)  Help
 
Enter a comma-separated list [x]: 2
 
        Selecting an Automatic Service Placement (ASP) Policy
 
Do you want the favored member to change to the one that is
specified when a manual relocation is performed (y/n/?): y
 
Enter 'y' to add Service 'disk1' (y/n): y
 
Adding service...
Starting service...
Saving the updated database...
Service successfully added...

6.4 Accessing Disk Services from Client Systems

To access a disk service that uses an Internet Protocol (IP) host name for a service name, client systems must include the disk service name and Internet address in their local /etc/hosts files.