C H A P T E R  4

Planning Your Storage Configuration

This chapter introduces you to the Sun StorageTek Common Array Manager storage components. It contains the following sections:

For more information about the concepts introduced in this chapter, see the appropriate topic in the online help.

Storage Array Configuration Components

The array management software configures both physical and logical storage components. The components of a storage array configuration are as follows.

In addition to the basic elements of your storage configuration covered in this guide, you can add advanced, premium features to your configuration. These features require the purchase of licenses. The following premium features are described in the online help and user guide:

Partitioning Storage Using Storage Domains

Storage domains, also called sets or storage partitions, enable you to partition storage to allow hosts or host groups access to specific volumes. Data hosts, such as a data base server, initiate data to store in volumes through the physical host ports (or initiators), residing on host HBAs. Volume-to-LUN mapping enables you to specify the host or host group that can access a specific volume on your storage array.

Note - Storage domains for LUN-mapping require the purchase and activation of a license. (Exception - the Sun StorageTek 6130 array includes some free storage domains to start.) The role of the free default domain is discussed below.

There is a free default domain with limited functions noted below. But to map specific initiators to specific volumes, you need to activate a premium license for a storage domain. Usually your need for premium licenses will be determined at the time you order your array.

The Default Domain

A non-premium, default storage domain exists to include the following:

Any volumes within the default storage domain can be accessed by all hosts and host groups within that storage domain.

Note - If you only use the default domain, you cannot configure software features such as profiles, pools, initiators, host groups, LUN-mapping, and virtual disks.

Premium Storage Domains

Premium storage domains define a volume-to-logical unit number (LUN) mapping, which will allow you to specify the host or host group that will have access to a particular volume in your storage array. The storage domain designates that only the selected host or host group has access to that particular volume through the assigned LUN.

When the storage domain consists of a volume mapped to a host group, it can enable hosts with different operating systems (heterogeneous hosts), to share access to a storage volume. A host within a host group can be mapped separately to a different volume.

A storage domain can contain up to 256 volumes. A volume can be included in only one storage domain and each LUN, from 0 to 255, can only be used once per storage domain.

Note: Not all operating systems support up to 256 LUN IDs. See the documentation for your operating system for more information.

FIGURE 4-1 shows how storage domains can be used to partition storage. It depicts a storage array configured with three storage domains, Storage Domain 1, Storage Domain 2, and Storage Domain 3.

FIGURE 4-1 Storage Array With Three Domains and Four Data Hosts

FIGURE 4-1 shows one host group and two hosts belonging to the same storage domain. A second host group has two hosts, each belonging to a separate storage domain.

Storage Domain 1 consists of two volumes, Marketing and Sales, that are mapped to Host Group X. Host Group X contains two hosts, Host A and Host B. All initiators associated with Host A and Host B, within Host Group X, have access to volume Marketing by way of LUN ID 1 and to volume Sales by way of LUN ID 2.

Storage Domain 2 consists of one volume, Engineering, that is mapped to Host Group Y. Host Group Y contains two hosts, Host C and Host D. By virtue of being associated with any host within Host Group Y, all initiators associated with Host C and Host D have access to volume Engineering by way of LUN ID 1.

Storage Domain 3 consists of one volume, Test, that is mapped to Host D. All initiators associated with Host D have access to volume Test by way of LUN ID 2. Note that Host D is a member of Host Group Y; however, since volume Test is mapped directly to Host D and not to Host Group Y, Host D is the only member of Host Group Y that can access volume Test.

Note - LUN IDs must be unique within a storage domain.

For more information about storage domains and LUN mapping, see the online help.

Best Practices - Storage Configuration

When configuring a storage array, you need to determine how to organize and allocate the total storage capacity into volumes and share those volumes among your data hosts. As you plan your storage configuration, it is important that you consider the following requirements for your site:

To combine disk mirroring with disk striping, configure RAID 1 with more than five drives. The firmware automatically creates a RAID 1+0 virtual disk.