Setting Up Disk Volume Sets

If both a Table of Contents and Search form are not displayed in separate frames along with this one, you may wish to redisplay this book in a frameset, beginning with the first page.

HP OpenVMS System Manager's Manual, Volume 1:...

Managing Storage Media

Mounting Volumes

Expanding Volumes Dynamically

Setting Up Disk Volume Sets

The following sections discuss concepts related to disk volume sets and explain how to perform the following actions:

Task Section

Create a disk volume set from new volumes
Creating a Disk Volume Set from New Volumes

Create a shadowed disk volume set
Creating a Shadowed Disk Volume Set

Create a disk volume set from an existing volume
Creating a Disk Volume Set from an Existing Volume and a New Volume

Add volumes to a disk volume set
Adding Volumes to an Existing Disk Volume Set

Task	Section
Create a disk volume set from new volumes	Creating a Disk Volume Set from New Volumes
Create a shadowed disk volume set	Creating a Shadowed Disk Volume Set
Create a disk volume set from an existing volume	Creating a Disk Volume Set from an Existing Volume and a New Volume
Add volumes to a disk volume set	Adding Volumes to an Existing Disk Volume Set

Understanding Disk Volume Sets

A volume set is a collection of disk volumes bound into a single entity by the DCL command MOUNT/BIND. To users, a volume set looks like a single, large volume. Volume sets have the following characteristics:

Files are automatically located anywhere on the volume set that space is available.

Disk quotas are enforced over the entire set.

A single directory structure covers the whole volume set.

Use a volume set to provide a large, homogeneous public file space. You must use a volume set to create files that are larger than a single physical disk volume. (The file system attempts to balance the load on the volume sets, for example, by creating new files on the volume that is the least full at the time.)

If you want several distinct areas of file storage, with different types of users or different management policies, you must use a separate volume or volume set for each area. For example, you might want one volume for permanent user storage, with limited disk quotas and regular backups. You might want another volume for "scratch" use, which means that the volume has liberal or no quotas and is not backed up; also, its files are purged on a periodic basis. Each separate volume or volume set must contain a top-level user file directory for each user who keeps files on that volume.

An advantage of separate volumes is their modularity. If one of the drives holding a volume set is out of service, the whole volume set is unavailable because of its interconnected directory structure. When a drive holding a single volume is not functioning, only the files on that volume are not available.

A disadvantage of volume sets is the large size of an image backup of a multivolume set, which might affect your backup schedule. For example, if backing up each of five separate volumes takes 5 hours in the evening, backing up these same volumes in a volume set will take 25 hours, which cannot be done overnight, thus possibly causing a scheduling problem.

Guidelines for Creating Disk Volume Sets

When planning disk volume sets, keep in mind the following points:

You can turn any single volume into a volume set by binding it with a newly initialized volume. Likewise, you can add another newly initialized volume to an existing volume set.

Do not include a system disk in a volume set.
Do not make the system disk part of a volume set because updates, upgrades, and optional product installations do not install correctly, and the operating system will no longer boot successfully.

You cannot bind two existing separate volumes containing files into a volume set. (The MOUNT command appears to let you do this, but the result is not a coherent volume set.)

Enter the MOUNT/BIND command only once to bind a volume set; thereafter, the volume set association is recorded on the volumes. (See Mounting Volumes for details.)

Once you bind two or more volumes into a volume set, you cannot separate them. The only way to separate a volume set is to use the Backup utility (BACKUP) to copy sets of directories selectively. (See Backing Up Files and Directories for more information.)

When you mount a disk volume set, the volume label specified in the list must correspond to a device name in the same position in the device name list.

You can bind two or more disk volumes into a volume set. The first volume in the set is called the root volume. Each volume in the set is identified by a volume number relative to the root volume, which is always relative to volume 1.

A disk volume set has a single directory structure. The master file directory (MFD) is on the first volume in the set.

When a disk volume set is on line and mounted, you can access all files and directories in the set by specifying either of the following names:

Device name of the device on which the root volume is mounted

Logical name assigned to the volume set when it was mounted

Using the /BIND Qualifier

Use the /BIND qualifier with the MOUNT command to create a disk volume set in the following format:MOUNT/BIND=volume-set-name

where:

volume-set-name
Specifies a 1- to 12-alphanumeric-character name identifying the volume set.

The volume set name must be different from all volume labels within the set, and all labels in the set must be unique.

The /BIND qualifier identifies a volume set by assigning it a volume set name that applies to all volumes in the set. The qualifier also identifies the root volume and creates the directory structure for the volume.

When you create files on a volume set, the file system allocates space for the files anywhere on the set, wherever the most space exists. When existing files on any volume are extended, extension occurs on the same volume unless the volume is physically full.

You can add new volumes to a volume set whenever additional space is needed. You can, for example, bind all disk volumes that are mounted into a volume set on a daily basis. Since this set contains all user file directories, users do not need to specify device names in file specifications to access files on any volume in the volume set. In fact, the physical location of a file is of no concern to users of the system.

Do not bind your system disk into a volume set. System software updates and optional product installations do not support volume sets. If certain system files move or extend to other volumes in the set, the system might fail to boot.

You do not need special privileges to create volume sets. However, you must have write access to the index file on all volumes you are attempting to bind into a volume set; this usually means you also must have a system UIC, have the user privilege SYSPRV, or be the owner of the volumes.

The following sections explain how to perform these tasks:

Task Section

Create a disk volume set from new volumes
Creating a Disk Volume Set from New Volumes

Create a shadowed disk volume set
Creating a Shadowed Disk Volume Set

Create a disk volume set from an existing volume and a new volume
Creating a Disk Volume Set from an Existing Volume and a New Volume

Add volumes to an existing disk volume set
Adding Volumes to an Existing Disk Volume Set

Expand a file system dynamically
Expanding Volumes Dynamically

Task	Section
Create a disk volume set from new volumes	Creating a Disk Volume Set from New Volumes
Create a shadowed disk volume set	Creating a Shadowed Disk Volume Set
Create a disk volume set from an existing volume and a new volume	Creating a Disk Volume Set from an Existing Volume and a New Volume
Add volumes to an existing disk volume set	Adding Volumes to an Existing Disk Volume Set
Expand a file system dynamically	Expanding Volumes Dynamically

Creating a Disk Volume Set from New Volumes

To create a disk volume set from new disk volumes:

Allocate the necessary devices and physically load the volumes.

Initialize each volume in the set.

When you initialize volumes for a volume set, you can use qualifiers with the INITIALIZE command to define the volume ownership and protection. Protection and ownership information is obtained from the root (first) volume. The protection and ownership of the other volumes is ignored.

Enter the MOUNT/BIND command to create the volume set. The MOUNT/BIND command both creates the volume set and mounts the volumes. When this command completes successfully, all volumes in the set are ready for use; in other words, you can now create user file directories.

Use the /BIND qualifier only once to create the volume set. Subsequently, you can mount the volume set with a single MOUNT command.

Examples

```
$ INITIALIZE DUA1: PAYVOL1
$ INITIALIZE DUA2: PAYVOL2
$ INITIALIZE DUA3: PAYVOL3
$ MOUNT/BIND=MASTER_PAY DUA1:, DUA2:, DUA3: PAYVOL1,PAYVOL2,PAYVOL3
```
This example assumes that the volumes to be bound contain no files or data. The INITIALIZE command initializes each volume in the set. The MOUNT/BIND command defines the volume set name, MASTER_PAY, and defines the relative volume numbers of the volumes PAYVOL1, PAYVOL2, and PAYVOL3.

The order of the device names corresponds to the volume labels specified: PAYVOL1 must be physically loaded on DUA1:, PAYVOL2 on DUA2:, and PAYVOL3 on the DUA3: device.

PAYVOL1, which is listed first in the list of labels, becomes the root volume of the set. The master file directory (MFD) for PAYVOL1 contains the directory structure for the entire volume set.

$ MOUNT DUA1:,DUA2:,DUA3: PAYVOL1,PAYVOL2,PAYVOL3

This example illustrates the use of one MOUNT command to mount a previously created volume set.

Creating a Shadowed Disk Volume Set

The following example illustrates one way to create a shadowed volume set.

$ MOUNT/BIND=TEST3013 DSA3011/SHADOW=($1$DUA402:,$1$DUA403:), 
DSA3012/SHADOW=($1$DUA404:,$1$DUA405:) TEST3011,TEST3012 TEST3013

This command creates a volume set with the logical name TEST3013. The volume set TEST3013 is shadowed, and each element of the shadowset (TEST3011 and TEST3012) is itself a volume set.

Creating a Disk Volume Set from an Existing Volume and a New Volume

To create a disk volume set from an existing volume and a new volume:

Use the DISMOUNT command to dismount the existing volume. Use the /NOUNLOAD qualifier to logically dismount the volume from the drive. (The volume, however, remains physically loaded on the drive.)

Use the INITIALIZE command to initialize the new volume, specifying the device on which the volume is to be mounted and the volume label.

Use the MOUNT/BIND command to bind the new volume to the existing volume, specifying the volume set name, the devices on which the volumes are mounted, and the volume labels.

Specify the volume label of the existing volume first; it becomes the root volume of the set. When you create a volume set from an existing volume, you must specify the label of the existing volume first because the file system must build on the existing directory structure.

Example

The following example shows how to create a disk volume set (called USERS) from an existing volume. In this example, the volume USERFILES already contains a directory structure and files; the volume is currently located on the DUA1: device. from existing volumes

         
$ DISMOUNT/NOUNLOAD DUA1:
$ INITIALIZE DUA2: USERFILES2
$ MOUNT/BIND=USERS DUA1:, DUA2: USERFILES, USERFILES2

In the MOUNT/BIND command, you must specify the existing volume label USERFILES before the volume label USERFILES2. USERFILES will be the root volume of the set.

If you attempt to create a volume set from two or more volumes that already contain files and data, the file system does not issue an error message when you enter the MOUNT/BIND command. However, the volumes are unusable as a volume set because the directory structures are not properly bound.

Adding Volumes to an Existing Disk Volume Set

You can add volumes to an existing volume set at any time. The maximum number of volumes in a volume set is 255.

This section contains examples that show how to add volumes to an existing volume set.

Examples

```
$ INITIALIZE DUA4: PAYVOL4
$ MOUNT/BIND=MASTER_PAY DUA4: PAYVOL4
```
In this example, the volume set named MASTER_PAY is on line and mounted and has volumes named PAYVOL1, PAYVOL2, and PAYVOL3.

The MOUNT/BIND command binds the volume PAYVOL4 with the existing volume set and makes the volume ready and available for use. Note that, if the volume set MASTER_PAY is mounted with the /SYSTEM, /GROUP, or /SHARE qualifier, the MOUNT/BIND command that adds a volume to the set must also specify the appropriate qualifier.

When you add a volume to an existing set, the only volume in the set that you must mount is the root volume, relative volume 1 (in this example, DUA4:). Mounting any of the other volumes is not necessary.

```
$ INITIALIZE DUA4: PAYVOL4
$ MOUNT/BIND=MASTER_PAY DUA1:, DUA2:, DUA3:, DUA4: -
_$ PAYVOL1, PAYVOL2, PAYVOL3, PAYVOL4/SYSTEM
```
In this example, a set named MASTER_PAY already exists, with volumes named PAYVOL1, PAYVOL2, and PAYVOL3.

You can add a volume to a set at the same time that you mount the volume set, as this example shows. Note that the first device/volume pair listed in the MOUNT/BIND command is the root volume of the set, the DUA1: volume. When you add a volume to a set while mounting the set, you must list the root volume first.

Mounting Volumes

Expanding Volumes Dynamically