This chapter is designed to help you choose your controller configuration. For the purposes of this chapter, a controller configuration consists of a set of containers that is managed and controlled by one or more controllers. The set of containers can include one or more of the following container types:

• Volume set
• Stripe set (RAID 0)
• Mirror set (RAID 1)
• RAID-5 set
• Volume set of stripe sets
• Volume set of mirror sets
• Stripe set of mirror sets (RAID 0/1)
• Volume set of RAID-5 sets

Criteria for Choosing a Controller Configuration

To choose the appropriate controller configuration, decide how important each of the following criteria is to meeting your data management and storage needs, and then refer to Table 1.

Random-Read Performance

The system's random-read performance is measured by its ability to locate and read data directly from a file without having to search sequentially from the beginning of the file. Applications that require high random-read performance include databases, transaction processing programs, and page files.

Random-Write Performance

A system's random-write performance is measured by its ability to write data directly to a file without having to search sequentially from the beginning of the file. Applications that require high random-write performance include databases, transaction processing programs, and page files.

Sequential-Read Performance

A system's sequential-read performance is measured by its ability to read large numbers of consecutive data elements. Applications that require high sequential-read performance include streaming video programs and backup/restore programs.

Sequential-Write Performance

A system's sequential-write performance is measured by its ability to write large numbers of consecutive data elements. Applications that require high sequential-write performance include streaming video programs and backup/restore programs.

Fault Tolerance

Fault tolerance is the ability of a system to recover from a failure of one or more disks without interrupting user or application access to data. Fault tolerance is used whenever data is more important than the cost of storing it.

Expansion

Expansion is the ability of a system to increase the available storage capacity (for example, the total capacity of a logical disk) for the operating system's file system. Most systems require expansion capabilities.

Load Balancing

Load balancing is the ability of a system to spread I/O across disks. Any I/O-intensive application benefits from load balancing.

Cost Per Usable Container Space

The cost per usable container space is the ability of the system to use all space in a container to store user data. (Unusable space includes parity in a RAID-5 set and the redundant half of a mirror set.)

Comparing Container Types

Use Table 1 to compare container types according to the criteria you rated in the previous section. In this table, values range from 1 (least useful) to 10 (most useful).

Note: For sequential-write performance, the ratings for stripe set and stripe set of mirror sets do not apply when both types of container have the same number of drives. In this case, a stripe set of mirror sets does not provide as much throughput as a stripe set because each stripe is smaller. Given the same number of drives, the ratings change to stripe set = 10 and stripe set of mirror sets = 8.

User Guide
Back to Contents Page Choosing Your Controller Configuration: Dell™ Flexible Array Storage Tool User's Guide	Criteria for Choosing a Controller Configuration	Comparing Container Types	Examples of Controller Configurations

Examples of Controller Configurations

The examples in this section show you how to use your system criteria to determine the optimum controller configuration for specific networking environments. You may find these examples useful in determining the controller configuration that best meets your needs.

Generally, when fault tolerance is required, a RAID-5 configuration is preferred because of the reduced overhead cost. Otherwise, a stripe set is appropriate.

Application Server

In the application server environment, users access applications from the server, but they store their data on their local hard disks. The controller configuration for this environment must provide high sequential-read performance.

Suggested controller configuration: Stripe set or, if fault tolerance is required, RAID-5 set or stripe set of mirror sets.

Developer-Environment Server

In a developer environment, users transfer data from the server to their local systems, modify the data, and return it to the server. The controller configuration for this environment must provide high random-read and random-write performance and fault tolerance.

Suggested controller configuration: RAID-5 set or stripe set of mirror sets.

Mail Server

In the mail server environment, when users log on to the server to read their mail, the server transfers the mail files to the user's local hard drive. The controller configuration for this environment must provide high random-read and random-write performance and fault tolerance.

Suggested controller configuration: RAID-5 set or stripe set of mirror sets.

Transaction Server

In a transaction server environment, such as a hospital or a bank, data availability is critical. Multiple PCs are connected to the server, and each user randomly accesses the server to create new files, update existing files, and read data. The controller configuration for this environment must provide high random-read performance and fault tolerance.

Suggested controller configuration: Stripe set of mirror sets.

Alternate controller configuration: Stripe set to store and manage data; mirror set to maintain a transaction log file.

Video Server

In a video server environment, users transfer large blocks of sequential data from the server, edit the data, and return the data to the server. The controller configuration for this environment must provide high sequential-read and -write performance.

Suggested controller configuration: Stripe set; if fault tolerance is required, RAID-5 set or stripe set of mirror sets.

Web Server

In a Web server environment, users log on to the server to locate and view information. Sometimes they enter data such as registration information, or transfer data if an FTP site allows it. The controller configuration for this environment must provide high sequential-read performance.

Suggested controller configuration: Stripe set; if fault tolerance is required, RAID-5 set or stripe set of mirror sets.