Reviewing Storage Architectures

Applies To: Windows Server 2003, Windows Server 2003 R2, Windows Server 2003 with SP1, Windows Server 2003 with SP2

When you plan a new storage configuration or reengineer your existing configuration, you will need to make decisions about the types of storage architecture to use. These architectures are direct-attached storage, network-attached storage, and storage area networks. The different storage architectures are not necessarily exclusive, but are actually complementary and often coexist on the same network. Because these architectures are well known, the discussion that follows includes only a brief overview of each architecture, and focuses on the planning considerations related to using each architecture with Windows Server 2003. The process for reviewing the storage architectures is shown in Figure 1.3.

Figure 1.3   Reviewing Storage Architectures

Direct-Attached Storage

Direct-attached storage refers to a storage device, such as a hard drive or tape drive, that is directly connected to a single computer. These connections are usually made by one of the following methods:

• Enhanced Integrated Drive Electronics (EIDE)

• Small Computer Systems Interface (SCSI)

• Fibre Channel

EIDE connects internal Advanced Technology Attachment (ATA) storage to a computer, SCSI provides a means to connect both internal and external storage to a computer, and Fibre Channel connects external storage to a computer. Fibre Channel is most often used with external storage in a SAN. Although Fibre Channel can be used for direct-attached storage, less expensive SCSI storage can offer similar performance, but works only over limited distances due to the physical limitations of the SCSI bus. When external direct-attached storage devices are located more than twelve meters away from a server, then Fibre Channel must be used.

Direct-attached storage retains its high popularity because of its low entry cost and ease of deployment. The simple learning curve associated with direct-attached storage technologies is also a factor many organizations consider. Direct-attached storage also makes it easy to logically and physically isolate data, because the data can only be directly accessed through a single server.

Although it is simple to deploy, there are other management considerations to take into account with direct-attached storage:

• Direct-attached storage can be more expensive to manage because you cannot redeploy unused capacity, which results in underutilization.

• Having storage distributed throughout the organization makes it difficult to get a consolidated view of storage across the organization.

• Disaster recovery scenarios are limited because a disaster will cause both server and storage outages.

• For data backup and recovery, you need to choose whether to attach local backup devices to each server, install dual network adapters in each server and back up the data over a separate LAN, or back up the server over the corporate LAN. Large organizations have found that placing stand-alone tape drives in individual servers can quickly become expensive and difficult to manage, especially when the number of servers in the organization grows into the hundreds. In this situation, it is often best to back up servers over a network to a storage library, which offers backup consolidation and eases management.

Network-Attached Storage

Network-attached storage solutions are ideal for both addressing immediate storage needs and storage consolidation projects. Their high capacity and ease of deployment allow you to implement network-attached storage with little planning. With network-attached storage, you can fulfill your storage requirements with a single purchase. This is because many network-attached storage devices are built to be appliances. Like home appliances, such as a refrigerator or microwave oven, you can literally purchase a network-attached storage appliance and plug it into your network. This is possible because network-attached storage appliances come prepackaged with network interfaces, storage interfaces (SCSI, Fibre Channel, or both), internal or external magnetic storage, and an operating system. Only the services required for file serving, security, and management are installed on the appliance, thus making it a high-performance file server. A network-attached storage implementation is shown in Figure 1.4.

Figure 1.4   Network-Attached Storage Implementation

Network-attached storage has risen in popularity primarily due to the quick-and-easy nature of its implementation: Many Windows Powered Network Attached Storage appliances can be installed and running within minutes, and easily integrate into any enterprise environment.

The operating systems on Windows Powered Network Attached Storage appliances are either Windows 2000 or Windows Server 2003. Windows Powered Network Attached Storage appliances offer the file system, security, reliability, and scalability features common to all Windows operating systems, and come preconfigured with network file system (NFS), File Transfer Protocol (FTP), AppleTalk, Hypertext Transfer Protocol (HTTP), Web Distributed Authoring and Versioning (WebDAV), and NetWare protocol support. Because Windows Powered Network Attached Storage appliances support other operating system environments such as UNIX and Linux, you can seamlessly integrate them into any existing computer infrastructure, whether it uses Windows or not. They also support standard Web protocols, which allows you to manage Windows Powered Network Attached Storage appliances from a Web browser.

Windows Powered Network Attached Storage appliances are well suited for use as both departmental file servers and enterprise file servers. Network-attached storage solutions built on Windows offer data protection and high availability features like clustering and snapshots. In addition, network-attached storage appliances offer a highly scalable solution that can grow with the business. For example, storage can be added on the fly to address growing business needs.

To summarize, the key benefits of Windows Powered Network Attached Storage are:

• Ease of deployment. Windows Powered Network Attached Storage appliances can be installed in a heterogeneous environment within minutes.

• Active Directory integration. Windows Powered Network Attached Storage appliances can be integrated with the Active Directory® directory service to take advantage of features such as Kerberos authentication, Internet Protocol security (IPSec), Encrypting File System (EFS), and Group Policy objects (GPOs).

• ISV utility support. You can install several independent software vendor (ISV) utilities on Windows Powered Network Attached Storage appliances, including quota, backup, antivirus, and replication utilities. This is not possible with many other network-attached storage appliances.

• Simple management. Remote management is supported through Terminal Services sessions as well as through a Web interface. Administrators do not have to learn a new operating system to operate a network-attached storage appliance, because it uses Windows 2000 or Windows Server 2003.

• Enhanced snapshot support. Windows Powered Network Attached Storage appliances maximize the availability of data by supporting up to 250 snapshots, which provides an advantage compared to other network-attached storage solutions. Snapshots are similar to the shadow copy feature in Windows Server 2003.

• DFS and FRS integration. You can use DFS to build and manage a single, hierarchical view of multiple file servers and their shares. To provide redundancy and load balancing, you can store shares with identical data on multiple servers, and DFS will automatically redirect clients to alternate servers if a server becomes unavailable. To keep these shares synchronized, you can use FRS.

For more information about Windows Powered Network Attached Storage appliances, see the Windows Powered Network Attached Storage link on the Web Resources page at https://www.microsoft.com/windows/reskits/webresources.

Storage Area Networks

Unlike direct-attached or network-attached storage, SANs require careful planning before implementation. SANs differ from network-attached storage in that they store and access data at the block level, whereas network-attached storage appliances store data at the file level. File level access is preferable for users and applications needing to access a particular file, whereas block level data access is better for applications that need to quickly access data. SANs also differ from other storage architectures in that they are dedicated storage networks, and use their own network protocols and hardware components.

A simple SAN configuration is illustrated in Figure 1.5.

Figure 1.5   SAN Implementation

For more information about specific considerations for deploying SANs with Windows Server 2003 see "Planning for SAN Deployment" later in this chapter.