Simplified Storage Migration for Microsoft Cluster Server Using VERITAS Volume Manager for Windows 2000 with Microsoft Cluster Server V E R I T A S W H I T E P A P E R June 2001
Table of Contents Overview...................................................................................1 Background: Microsoft Cluster Server and Dynamic Disks.................................................2 Microsoft Cluster Server.......................................................................2 Dynamic Disks in Windows 2000................................................................2 VERITAS Volume Manager for Windows 2000.......................................................3 VERITAS Volume Manager and MSCS...............................................................4 Multiple configurable disk groups................................................................4 Disk groups without auto-import..............................................................4 The quorum disk group.......................................................................4 Resource DLL...............................................................................5 Volume Manager Cluster Administrator Extension....................................................5 Configuring Storage Migration for Microsoft Cluster Server...............................................6 Summary...................................................................................7
Overview Windows 2000, the next generation of the Windows NT operating system technology, offers significant advances in performance, scalability, and manageability. One of the key features of the new operating system is the Logical Disk Manager that provides logical volume management and online disk administration capabilities. VERITAS Volume Manager for Windows 2000 extends these in-the-box basic capabilities to create a highly scalable, manageable platform for the most data-intensive or critical application environments. Windows 2000 also supports Microsoft Cluster Server (MSCS), the Microsoft solution for creating a loosely coupled configuration of servers with application failover capabilities. The MSCS technology has been in place for a few years and is used to improve the availability and manageability of NT systems. Using VERITAS Volume Manager for Windows 2000, system administrators can create flexible storage configurations integrated with the MSCS cluster design, so that the Cluster Server can automatically migrate all the storage required for a specific application between nodes when a failover occurs. This solution combines the high-availability failover capabilities of the Microsoft Cluster Server with the highly configurable and manageable storage capabilities of VERITAS logical volume management support. The VERITAS volume management technology introduces the concept of disk groups to the Windows platform. A disk group is a collection of disks containing arbitrary volume layout. This allows system administrators to group storage by need. For example, all the storage used by the engineering department goes into one group, all the storage used by the finance group goes into another, and so on. This is a powerful abstraction for virtualizing storage in a Storage Area Network (SAN). The disk group is the entity that fails over in an MSCS environment. The volume manager in Windows 2000 supports only one disk group. All disks on a Windows 2000 system, including the boot disk, exist in this group. The VERITAS Volume Manager for Windows 2000 supports multiple disk groups, thus supporting an MSCS environment. This paper provides a brief overview of the various components involved in this solution and then discusses specifically how to create application-specific storage migration for MSCS using VERITAS Volume Manager. This paper is intended for system administrators or others familiar with the Windows environment. More information on Windows 2000 is on the Microsoft Web site (www.microsoft.com). The VERITAS Web site (www.veritas.com) contains other sources of information on VERITAS Volume Manager and Volume Manager for Windows 2000. www.veritas.com Using VERITAS Volume Manager for Windows 2000 with Microsoft Cluster Server Page 1
Background: Microsoft Cluster Server and Dynamic Disks This section briefly describes the key components of the MSCS clustering solution on Windows 2000: Microsoft Cluster Server, Windows 2000 dynamic disks, and the VERITAS Volume Manager for Windows 2000. Microsoft Cluster Server Microsoft Cluster Server (MSCS) is the Microsoft clustering solution for Windows servers. A detailed description of MSCS is beyond the scope of the paper, but is on the Microsoft Web site. This section highlights some relevant points. Microsoft Cluster Server employs a shared nothing architecture, and was initially introduced as a two-node clustering solution for the Enterprise Edition of Windows NT. As of this writing, MCSC is supported with two nodes in Windows 2000 Advanced Server version, and with two or four nodes in Windows 2000 Datacenter Server version. The primary operating attributes of MSCS are as follows: Each system in the cluster is a node. Today the nodes must be NT server or Windows 2000 systems. Both nodes should be the same OS level. Any item managed by the Cluster Server is a resource. Resources may include storage devices, file shares, TCP/IP addresses, applications, and databases. A resource group is the collection of resources that fail over as a group. All resource dependencies (such as a net name that depends on an IP address) must exist in the same group. Shared nothing refers to the fact that resources such as storage belong to only one system in the cluster at any time. However, the storage is physically connected to both nodes via SCSI bus or Fibre Channel. In the event of a failure on one node, the other node can import the storage resource and host the application. This cluster design brings both availability and manageability benefits. The MSCS software tracks the state of the nodes in the cluster. In the event of an application or server failure, it either restarts the application or performs a failover to an available node. When the failed node is again available, MSCS switches the applications back to their preferred node. Most stateless applications switch to the failover node transparently. Some applications that track the state of the nodes need to re-establish a connection to the cluster. Otherwise, the failover is transparent. System administrators can also manually move services from one node to another to perform system maintenance tasks without resorting to downtime on production applications. Dynamic Disks in Windows 2000 VERITAS worked with Microsoft to develop the logical volume management in the Windows 2000 software. Logical volume management removes physical limitations of storage, enabling administrators to build higher-performance, more available storage configurations from existing disk devices and simplifying disk administration tasks for reduced cost of ownership. Windows 2000 introduces a new disk management (DM) facility that supports both basic and dynamic disks. Basic disk uses standard disk partition tables and has been supported on previous versions of Windows. Dynamic disk stores disk and volume information on the disk itself. Dynamic disks in Windows 2000 can host software-managed volumes called dynamic volumes. Because the disk and volume information is on the disk itself instead of in system tables, moving or reallocating dynamic disk storage between systems is easier. Another major benefit is that administrators can perform disk and volume management tasks without restarting the system. The volume manager supports online growth and management of storage. Page 2 Simplified Storage Migration for Microsoft Cluster Server www.veritas.com
Dynamic volumes in Windows 2000 may be simple, spanned, striped, mirrored, or RAID-5 (striping with distributed parity). The Windows 2000 Disk Manager provides online management and configuration of local and remote disk storage and a domain-wide view of storage resources. Together, these features support highly configurable and manageable storage solutions. VERITAS Volume Manager for Windows 2000 VERITAS Volume Manager for Windows 2000 extends the capabilities of Windows 2000 dynamic disks. For example, a VERITAS Volume Manager dynamic disk has all the capabilities of the native dynamic disk, plus: Striped and RAID-5 volumes using more than 32 columns Mirrored stripe volumes for a high-performance, highly available storage solution N-way mirroring administrators can create and detach third mirrors to mirrored volumes Preferred plex designating a local mirror as the preferred read device for data with heavy request loads. VERITAS Volume Manager for Windows 2000 also provides advanced online management capabilities. For example, administrators can expand mirrored, striped, and RAID-5 volumes while the data is online and available. Administrators can use the graphical interface to identify storage bottlenecks and move data to correct or prevent performance problems. Finally, VERITAS Volume Manager supports shared and segmented storage configurations using the concept of multiple disk groups. This makes it easier for multiple Windows servers to share a disk farm or Storage Area Network by segmenting the storage available, with each server owning specific storage segments. The administrator can easily reconfigure or change the segmentation. This last feature is relevant for supporting storage migration with MSCS. www.veritas.com Using VERITAS Volume Manager for Windows 2000 with Microsoft Cluster Server Page 3
VERITAS Volume Manager and MSCS VERITAS Volume Manager provides a number of features to enable storage migration with MSCS. These include: The ability to create multiple, application-specific disk groups A resource Dynamically Linked Library (DLL) that defines these logical volume resources for MSCS A client extension to the MSCS graphical user interface (GUI). This section describes these features and how they contribute to storage migration with MSCS. Multiple configurable disk groups A disk group is a configurable set of disks. With the native Windows 2000 support, you have only one disk group of dynamic disks. Using VERITAS Volume Manager for Windows 2000, you can define multiple disk groups. This is particularly useful for situations in which storage is connected to a shared disk bus. Using disk groups to identify the physical devices belonging to a specific application makes it easier to relocate or reconfigure storage. Administrators can use segmentation to share a large disk farm (or storage area network) between several servers. By allocating storage into disk groups, administrators can track which storage belongs to which applications or servers without any physical reconfiguration. Disk groups without autoimport In the event of a server failure, the MSCS software determines the state of the cluster and then starts resources accordingly; contention algorithms prevent both nodes from each restarting a separate version of the cluster. By default, Volume Manager automatically imports disk groups when the server restarts. VERITAS Volume Manager for Windows 2000 can create disk groups that are not automatically imported to the server but wait for the Cluster Server to import the data for the appropriate node. The quorum disk group Volume Manager for Windows 2000 supports the concept of a disk group as quorum resource. Exactly one quorum resource is in every cluster. A quorum resource, in MSCS, is a resource that determines ownership of the cluster. In a way, the quorum resource is a global control lock for the cluster. The quorum is also used to determine which node is the cluster when the network heartbeat is lost. This prevents split-brain situations when the connection between the nodes is broken and both nodes try to start the cluster. To own a quorum disk group, the server must successfully import the disk group and must be able to obtain a SCSI reservation on a majority of the disks in the disk group. For this reason, VERITAS recommends that you always use odd numbers of disks in the quorum disk group. The quorum disk group is critical to the system; a three-way mirror strategy provides high levels of redundancy and prevents a deadlock situation because it contains an odd number of devices. SCSI reservations are placed on all disks in a disk group to physically fence off the disks from other nodes in the cluster. Page 4 Simplified Storage Migration for Microsoft Cluster Server www.veritas.com
Resource DLL MSCS resources are implemented as Dynamically Linked Libraries (DLLs) managed by the MSCS Resource Monitor. Microsoft publishes the resource DLL interfaces in a Cluster software development kit. VERITAS Software used these published interfaces to create resource DLLs for managing Volume Manager cluster disk groups and includes these in the Volume Manager for Windows 2000 product. Volume Manager Cluster Administrator Extension VERITAS Volume Manager for Windows 2000 also provides an extension to the Microsoft Cluster Administrator graphical user interface to support managing Volume Manager disk groups as MSCS resources. Administrators can use Volume Manager cluster administrator extension interface to create disk group resources and display the properties of the existing disk group resources. Figure 1: List of available Volume Manager Cluster Disk Groups and Cluster Disk Group Resource Properties www.veritas.com Using VERITAS Volume Manager for Windows 2000 with Microsoft Cluster Server Page 5
Configuring Storage Migration for Microsoft Cluster Server This section provides an overview of the process of configuring VERITAS Volume Manager to support storage migration with MSCS. It assumes that you are using Windows 2000 and VERITAS Volume Manager for Windows 2000. The Microsoft Cluster Server Configuration Wizard automatically detects any available cluster resources. For this reason, you should create the cluster disk groups you plan to use before configuring MSCS. Any standard (non Volume Manager) dynamic disks created on Windows 2000 will not be available as cluster resources. 1. Create VERITAS Volume Manager dynamic disks to support the storage that will be used in the cluster. 2. Create disk groups and logical volumes. Volume Manager provides a Microsoft Management Console (MMC) snap-in interface, with a centralized view of domainwide storage and wizards to guide disk-management operations. When creating disk groups, indicate that they will be cluster disk groups (without the auto-import feature enabled). When creating the quorum disk group, be sure to use an odd number of disks. Three-way mirroring ensures both availability and consistency. 3. Install MSCS; this instantiates the Volume Manager resources. You will be asked to identify resource dependencies during installation. 4. Run the Microsoft Cluster Administrator. At this point, all VERITAS cluster disk groups will be discovered and available from the interface. Page 6 Simplified Storage Migration for Microsoft Cluster Server www.veritas.com
Summary VERITAS Volume Manager for Windows 2000 builds on the strong foundation of logical volume management and dynamic disks in Windows 2000. It provides advanced storage-management capabilities for applications with critical performance or availability requirements and offers the highest level of online disk- and volume-management capabilities available. In addition, VERITAS Volume Manager for Windows 2000 provides the ability to migrate application-specific storage between nodes in an MSCS cluster. Using Volume Manager and MSCS together provides a flexible, inexpensive clustering solution that uses commodity hardware and provides a great deal of flexibility and manageability. www.veritas.com Using VERITAS Volume Manager for Windows 2000 with Microsoft Cluster Server Page 7
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