07-04-2009, 09:05 PM
Design Of Cluster Logical Volume Manager
In an open systems environment, logical volume manager (LVM) virtualizes storage by consolidating physical storage into logical volumes, which are available to applications or file systems. LVMs are available on most Unix platforms (including Linux) and on Windows 2000. By assembling virtual storage volumes out of numerous physical devices, you can create storage configurations tuned for specific applications, without the limitations of specific hardware devices. Instead, you can make use of the available storage, without locking into proprietary storage solutions. Logical volume managers improve application availability by building redundancy into the logical volume itself. The possibilities go beyond simple mirroring and RAID. For example, the failure of a device in a redundant storage configuration can degrade performance and expose the data to risk from another failure. The logical volume manager can maintain a pool of spare disks that can be automatically swapped in (hot relocation) when a device fails in a logical volume. It can even move data back automatically when the failed device is replaced or repaired. Unlike a physical device, a logical volume has a nearly limitless capacity: Administrators can add storage as needed without interrupting access to the data. When used with a database's auto-extend capabilities or a file system's automatic extension, a logical volume manager can significantly ease the problem of provisioning storage for growing applications.
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