Creating Volumes

To create a volume with a specified length, specify the make keyword to vxvoladm as shown here:

It is possible to specify a combination of capabilities, templates and rules to this command. Recall that:

• A rule specifies a criterion for choosing and allocating storage.
• A template is a meaningful collection of rules that define a capability.
• A capability is a high-level description of what a volume can do.

The properties of the volume that is created are further determined by any parameters and other attributes that you specify. Rules, capabilities and templates may be combined as follows:

• If you specify rules along with capabilities, ISP creates volumes that comply to the rules that are defined in the capabilities, and also to those rules that you specify as arguments to vxvoladm.
• If you specify rules along with templates, ISP creates volumes that comply to the rules in the templates, and also to those rules that are specified as arguments to vxvoladm.
• If you specify capabilities along with templates, ISP selects the appropriate templates from those specified that conform to the desired capabilities.
• If you specify rules, capabilities and templates, ISP selects the appropriate templates from those specified that conform to the desired capabilities, and that adhere to the specified rules in addition to the rules in those templates.

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  Note    Refer to Using Capabilities, Templates and Rules for more information.

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Finally, you can create volumes by specifying user templates that you have set up with the required redundancy, fault tolerance, or performance capabilities for the applications that you run at your site. See Creating and Modifying User Templates for more information.

Creating Volumes by Specifying Capabilities

A capability is a high-level description of a volume, for example, DataMirroring, Striping or PrefabricatedRaid5. ISP automatically selects a suitable template from those that provide the desired capability. As such, this is the most abstract way of creating volumes using vxvoladm as it requires the least specification by you. You can customize a capability by specifying values for any variable parameters that it defines.

For a list of predefined capabilities that are supported, see Capabilities. The following sections provide some examples of creating volumes with these capabilities.

Creating a Mirrored Volume

The following command creates a 1-gigabyte volume with the default number of 2 mirrors:

The init=active attribute makes the volume immediately available for use without attempting to synchronize its empty plexes.

The following command creates a 1-gigabyte volume with 3 mirrors:

Creating a Mirrored Volume with Mirrors on Separate Enclosures

The following command creates a 2-gigabyte mirrored volume with 2 mirrors, and with the mirrors located on separate enclosures:

Such a volume tolerates the failure of one enclosure and provides greater reliability. Such a capability can be combined with multipathing to provide resilience against the failure of one of the paths to an enclosure:

Creating a Striped Volume

The following command creates a 2-gigabyte striped volume with 10 columns:

Creating a Mirrored-Stripe Volume with Mirrors on Separate Controllers

The following command creates a 2-gigabyte mirrored-stripe volume with 8 columns, and with the mirrors located on separate controllers:

Creating a Striped-Mirror Volume from Prefabricated Mirrors

The following command creates a 10-gigabyte striped-mirror volume with 8 columns, and which uses prefabricated mirrors that are exported by an array to form each column:

Creating a RAID-5 Volume with a RAID-5 Log

The following command creates a 2-gigabyte RAID-5 volume with 8 data columns and a RAID-5 log that has 2 redundant copies:

Creating Volumes by Specifying Capabilities and Rules

You can specify storage selection and layout rules in addition to capabilities when creating volumes. This allows you to select explicitly which storage can and cannot be used for certain volumes. For example, you might do this to ensure that volumes are created on storage with certain performance or reliability that is implemented in an array's hardware.

Refer to Rules for details of the different types of rule and their usage.

Creating a RAID-5 Volume on Prefabricated Storage

The following command creates a 10-gigabyte volume on a prefabricated RAID-5 disk that is exported from an array made by a specified vendor:

Creating a Mirrored Volume on Enclosures in Separate Locations

The following command creates a mirrored volume that tolerates the failure of a single enclosure, where each enclosure is in a different room. This avoids single point of failure and ensures greater reliability.

Creating a Striped Volume Excluding Certain Disks

The following command creates a striped volume on storage other than that in Room1 and certain disks in enclosure, Enc1:

Creating Volumes by Specifying Templates

Volumes can be created by specifying templates instead of capabilities. The following example demonstrates how to create a mirrored volume using a template:

A template can refer to other templates in following ways:

• It can be an extension of another template.
• It can apply another template.
• It can require or inherit a capability that is provided by another template.

If one or more of these conditions apply, ISP may not be able to use the given templates and volume creation may fail. To view the details of a template, use the following command:

Examine the definitions of the extends, inherits, requires and apply fields to see the other templates on which the specified template depends. See Volume Templates for more information about these fields.

For example, the following command fails because of a template dependency:

The vxtemplate command is then run to examine the definition of the PrefabricatedRaid5 volume template:

The apply rule in the listing shows that the PrefabricatedRaid5 template depends on the ArrayProductId template. If the ArrayProductId template does not depend on any other templates, the vxvoladm make command should be modified to list ArrayProductId in addition to PrefabricatedRaid5:

Creating Volumes by Specifying Templates and Rules

The following command creates a striped volume using a template, and specifies a rule to ensure that storage is allocated only from a single enclosure in a specified location:

Creating Volumes by Specifying Templates and Capabilities

If you specify templates in addition to capabilities when creating a volume, this restricts ISP to choosing from the specified templates.

The following example shows how to specify both capabilities and templates:

If you specify rules in addition to capabilities and templates, these rules are applied after ISP has selected the templates that satisfy the required capabilities.

Creating Volumes by Specifying User Templates

Once you have set them up, user templates provide the simplest way of creating volumes for use with the applications that you run. For example, you can configure user templates that ensure that volumes that you create to store database tables all share the same reliability and performance capabilities, and that they are allocated from a restricted set of storage. The following example shows how you might use a user template to create a volume for a database table: