Tuesday, July 5, 2011

Building Fault-Tolerant Windows Server 2008 R2 Systems - Designing Fault-Tolerant Server Disks

Many Windows Server 2008 R2 systems that will be used for NLB or failover clusters are deployed with local disk storage. The local disks commonly store the operating system files as well as the necessary service or application files. Each system that will participate in a cluster should have the local disks and volumes configured exactly the same, including drive letters and any mount point assignments. When local disks are used to provide the operating system and application or service core files, the local disks should be deployed using redundant, fault-tolerant configurations. There are mainly two different ways to add fault tolerance to the local disks in a Windows Server 2008 R2 system. The first is creating redundant arrays of inexpensive disks (RAID) using disk controller configuration utilities (also known as hardware-level RAID), and the second is creating RAID volumes using dynamic disks using the Disk Management console from within the operating system (known as software-level RAID).

Using two or more disks, different RAID-level arrays can be configured to provide fault tolerance that can withstand disk failures and still provide uninterrupted disk access. Implementing hardware-level RAID configured, stored, and managed by the system’s disk controllers is preferred over the software-level RAID configurable within Windows Server 2008 R2. Windows Server 2008 R2 dynamic disk mirrored and RAID-5 volumes are managed by the system and add some load to the system. Additionally, another good reason to provide hardware-level RAID is that the configuration of the disks does not depend on the operating system, which gives administrators greater flexibility when it comes to recovering server systems and performing upgrades. For more information on disk configuration options, refer to Chapter 28 of this book. For detailed information on how to best configure RAID arrays using local disk controllers, refer to the manufacturer’s documentation.

As a best practice, Windows Server 2008 R2 can be deployed with the operating system disks stored on RAID-1, or mirrored, disks and presented to the operating system as the “C” volume. A second volume in the system can be used to store application data and files and, when possible, this data should be placed on different redundant disks or at least on separate volumes to prevent impact to the space available in the operating system volume.

Source of Information : Sams - Windows Server 2008 R2 Unleashed (2010)

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