How RamDisk and RamDisk Plus® Work in a Microsoft Cluster

   

In clustered and non-clustered environments, each server (or host) runs its own instance of an operating system, services and applications. Each server owns and manages the physical and virtual devices local to it.

   

However, in a server cluster, there are an additional set of resources managed and shared between the various servers, or nodes, belonging to the cluster. The nodes share resources such as network addresses, physical disks, file shares, etc. Microsoft® Server Cluster Service (MSCS) and Windows Server Failover Clustering (WSFC) manage these shared resources and make them available to cluster applications.

Disk data in RAM achieves the fastest access possible
  As a general rule, when an application is run in a cluster, its data is stored on one or more cluster disks – disks shared between the nodes in the cluster. Whether the application’s data is persistent or temporary, it is commonly located on persistent storage. Locating temporary data on persistent storage frequently results in degraded application performance.
    In those cases where cluster application performance is constrained by I/O access to temporary data (a common occurrence with SQL), performance may be improved through the use of a RAM disk. By locating temporary application data on a RAM disk, access to the data is accelerated, resulting in higher application performance.
RAM disk as a local device  

A RAM disk implemented with main memory is a local device, and so ordinarily it would not be available as a cluster resource. However, SuperSpeed’s RamDisk and RamDisk Plus products seamlessly integrate RAM disks into the MSCS and WSFC clustering environments through the use of a proprietary cluster resource DLL. In effect, the cluster environment ‘sees’ a single RAM disk resource available in the cluster. This high-performance storage resource can be made available to any cluster application.

Note: A single RAM disk cluster resource requires that a corresponding RAM disk device be present on each node in the cluster. This is because a physical RAM disk device is not physically shared, but logically shared through the cluster management software.
   

When the RAM disk cluster resource is brought online, a cluster application is able to access the local RAM disk. In this way, the RAM disk, although a local resource, is made available to the cluster application hosted on the local node.

RamDisk and RamDisk Plus can create RAM disk devices sized up to 16 TB. The RAM disks are created early in system startup, and are available to services and applications as soon as they start. Where desired, a RAM disk can be initialized with an empty file system, with populated file system, or even as a RAW device (no file system). By placing temporary data on the RAM disk, all read and write access to that data occurs at the highest rates possible, typically some fifty times the rates of disk access.

See Also:
How to implement RamDisk or RamDisk Plus® in a Microsoft Cluster
Accelerating Application Performance in a Cluster
How to Relocate Microsoft SQL Server's tempdb Files

How the Microsoft Server Cluster Service (MSCS) Works
How Windows Server Failover Clustering (WSCS) Works

 

Last updated 18 January 2012


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