This section describes the main motivators that drive storage area network (SAN)
implementations, and present some of the key benefits that this technology might bring to data-dependent business.
2.1.1 The problem
Distributed clients and servers are frequently chosen to meet specific application needs. They might, therefore, run different operating systems (such as Windows Server, various UNIX offerings, IBM VMware vSphere, VMS). They might also run different database software (for example, IBM DB2®, Oracle, IBM Informix®, SQL Server). Therefore, they have different file systems and different data formats.
Managing this multi-platform, multivendor, networked environment is increasingly complex and costly. Software tools for multiple vendors and appropriately skilled human resources must be maintained to handle data and storage resource management on the many differing systems in the enterprise. Surveys that are published by industry analysts consistently show that management costs that are associated with distributed storage are much greater. The costs are shown to be up to 10 times more than the cost of managing consolidated or centralized storage. This comparison includes the costs of backup, recovery, space management, performance management, and disaster recovery planning.
Disk storage is often purchased from the processor vendor as an integral feature. It is difficult to establish if the price you pay per gigabyte (GB) is competitive, compared to the market price of disk storage. Disks and tape drives, directly attached to one client or server, cannot be used by other systems, leading to inefficient use of hardware resources. Organizations often find that they need to purchase more storage capacity, even though free capacity is available in other platforms.
Additionally, it is difficult to scale capacity and performance to meet rapidly changing
requirements, such as the explosive growth in server, application, and desktop virtualization. There is also the need to manage information over its entire lifecycle, from conception to intentional destruction.
Information that is stored on one system cannot readily be made available to other users. One exception is to create duplicate copies and move the copy to the storage that is attached to another server. Movement of large files of data might result in significant degradation of performance of the LAN and WAN, causing conflicts with mission-critical applications. Multiple copies of the same data might lead to inconsistencies between one copy and another. Data that is spread on multiple small systems is difficult to coordinate and share for enterprise-wide applications. Some examples of this type of application include: E-business, enterprise resource planning (ERP), data warehouse, and business intelligence (BI).
Chapter 2. Why and how we can use a storage area network 17
New ways must be found to control costs, improve efficiency, and simplify the storage infrastructure to meet the requirements of the modern business world.
2.1.2 The requirements
With this scenario in mind, there are a number of requirements that the storage
infrastructures of today might consider. The following factors are some of the most important requirements to consider:
Unlimited and just-in-time scalability: Businesses require the capability to flexibly adapt to the rapidly changing demands for storage resources without performance degradation.
System simplification: Businesses require an easy-to-implement infrastructure with the minimum amount of management and maintenance. The more complex the enterprise environment, the more costs that are involved in terms of management. Simplifying the infrastructure can save costs and provide a greater return on investment (ROI).
Flexible and heterogeneous connectivity: The storage resource must be able to support whatever platforms are within the IT environment. This resource is essentially an
investment protection requirement that allows for the configuration of a storage resource for one set of systems. It later configures part of the capacity to other systems on an as-needed basis.
Security: This requirement guarantees that data from one application or system does not become overlaid or corrupted by other applications or systems. Authorization also requires the ability to fence off the data of one system from other systems.
Encryption: When sensitive data is stored, it must be read or written only from those authorized systems. If for any reason the storage system is stolen, data must never be available to be read from the system.
Hypervisors: This requirement is for the support of the server, application, and desktop virtualization hypervisor features for cloud computing.
Speed: Storage networks and devices must be able to manage the high number of gigabytes and intensive I/O that is required by each business industry.
Availability: This is a requirement that implies both the protection against media failure and the ease of data migration between devices, without interrupting application processing. This requirement certainly implies improvements to backup and recovery processes. Attaching disk and tape devices to the same networked infrastructure allows for fast data movement between devices, which provides enhanced backup and recovery capabilities, such as:
– Serverless backup. This is the ability to back up your data without using the computing processor of your servers.
– Synchronous copy. This ensures that your data is at two or more places before your application goes to the next step.
– Asynchronous copy. This ensures that your data is at two or more places within a short time. It is the disk subsystem that controls the data flow.
In the following section, we describe the use of SANs as a response to these business requirements.