Multihost storage makes disks highly available by connecting the disks to multiple nodes. Multiple nodes enable multiple paths to access the data, if one path fails, another one is available to take its place.
Multihost disks enable the following cluster processes:
Tolerating single-node failures.
Centralizing application data, application binaries, and configuration files.
Protecting against node failures. If client requests are accessing the data through a node that fails, the requests are switched over to use another node that has a direct connection to the same disks.
Providing access either globally through a primary node that “masters” the disks, or by direct concurrent access through local paths.
A volume manager enables you to manage large numbers of disks and the data on those disks. Volume managers can increase storage capacity and data availability by offering the following features:
Disk-drive striping and concatenation
Disk-drive hot spares
Disk-failure handling and disk replacements
Sun Cluster systems support the following volume managers:
Solaris Volume Manager
VERITAS Volume Manager
Sun StorEdge Traffic Manager software is fully integrated starting with the Solaris Operating System 8 core I/O framework. Sun StorEdge Traffic Manager software enables you more effectively to represent and manage devices that are accessible through multiple I/O controller interfaces within a single instance of the Solaris operating environment. The Sun StorEdge Traffic Manager architecture enables the following:
Protection against I/O outages due to I/O controller failures
Automatic switches to an alternate controller upon an I/O controller failure
Increased I/O performance by load balancing across multiple I/O channels
Sun Cluster systems support the use of hardware Redundant Array of Independent Disks (RAID) and host-based software RAID. Hardware RAID uses the storage array's or storage system's hardware redundancy to ensure that independent hardware failures do not impact data availability. If you mirror across separate storage arrays, host-based software RAID ensures that independent hardware failures do not impact data availability when an entire storage array is offline. Although you can use hardware RAID and host-based software RAID concurrently, you need only one RAID solution to maintain a high degree of data availability.
Because one of the inherent properties of clustered systems is shared resources, a cluster requires a file system that addresses the need for files to be shared coherently. The Sun Cluster file system enables users or applications to access any file on any node of the cluster by using remote or local standard UNIX APIs. Sun Cluster systems support the following file systems:
UNIX file system (UFS)
Sun StorEdge QFS file system
VERITAS file system (VxFS)
If an application is moved from one node to another node, no change is required for the application to access the same files. No changes need to be made to existing applications to fully utilize the cluster file system.