Preliminary considerations |
|
Before starting the installation process, we recommend giving due
consideration to each of the following points:
- The RAM disk’s size and drive letter,
- The name and location of the folder to serve as the RAM disk’s
mount point,
- The impact of reduced available system memory on the cluster application,
- On a production cluster, a convenient time when the cluster application
can be stopped
|
RAM disk size and
drive letter |
|
Determining the RAM disk’s size is an important consideration.
If the size is too large, unused memory will not be available to the
application and other system components, effectively wasting the resource.
If the size is too small, the performance benefit will be reduced, or
the application may even fail to start. The appropriate amount to allocate
varies from application to application.
The drive letter to be assigned to the RAM disk must be unassigned
on all cluster nodes. Make sure it is not assigned to a network drive,
which some tools may display as unassigned. |
RAM disk mount point
folder |
|
 The
RAM disk itself is not a cluster resource; it resides on and belongs to
the local node. To make it available to the cluster application, the local
RAM disk is mounted on a folder that resides on a shared physical disk.
The physical disk must be part of the target cluster application’s
group, and contain an accessible NTFS volume.
On the selected NTFS volume, an empty folder should be created to be
used by the RAM Disk cluster resource. When the resource is brought
online, the RAM disk will be mounted at that folder, and all I/O directed
at that folder will be realized on the local RAM disk.
Take note of the cluster resource name of the physical disk hosting
the NTFS volume, as the RAM Disk cluster resource must be made dependent
on it. |
Impact of reduced
available system memory on the cluster application |
|
When
memory resources currently allocated to the cluster application are reduced,
the typical impact is a reduction in overall performance. To make up for
the loss, the resources must be reallocated to the system’s bottleneck
in an effective manner. Where a system is bottlenecked by access to temporary
data, a RAM disk is an effective performance solution.
However, over-allocation of memory resources to the RAM disk can result
in a lower overall performance. Frequently, it is necessary to experiment
with different allocation sizes to find the best balance and optimize
performance. |
Stopping the cluster
application |
|
The
cluster application must be made dependent on the RAM Disk cluster resource.
This cluster dependency cannot be configured while the application is
running – it must be stopped.
Most cluster applications’ configuration settings include limits
on memory resource allocations. These settings may have to be reduced
to free system memory for the RAM disk’s allocation. In order
to take effect, the application must be stopped to free its resources,
the configuration setting changed, and the application restarted afterwards.
Additionally, to take advantage of the RAM Disk cluster resource, the
application must be reconfigured to place its temporary data in the
file system folder where the RAM disk will be mounted. Once again, this
change requires that the application be stopped, reconfigured, and restarted. |
How
to Implement a RAM Disk in a Cluster |
| 1. |
Install RamDisk or RamDisk Plus (version 8.0.3 or greater) on each cluster
node. To install successfully, the cluster service must be running on
the node. |
| 2. |
Stop the cluster application. |
| 3. |
Add a local RAM disk to each cluster node. (Use the same parameters
on each node.)
| a. |
Select a size to large enough to contain the temporary data. |
| b. |
Select an appropriate drive letter. |
| c. |
Select "NTFS" file system, without compression. |
| With RamDisk Plus: |
| d. |
Use the default image location. |
| e. |
Do not enable "Save at system shutdown" or "Reserve
space for full disk". |
|
| 4. |
Create a folder in an NTFS volume on a shared cluster disk to serve
as the mount point for the local RAM disk. |
| 5. |
Create a RAM Disk cluster resource.
| a. |
On the first page of the "New Resource" wizard, enter
the name of the new RAM Disk resource, and select the cluster group
to which it will belong. |
| b. |
Navigate through the wizard, setting the appropriate dependencies,
etc. Be sure to set the RAM Disk resource as dependent on the physical
disk resource which contains the folder to be used as a mount point. |
| c. |
On the last wizard page "RAM Disk Cluster Resource Parameters",
enter the fully-qualified path to the folder previously created
in step 4. The path must include a trailing backslash (\). |
|
| 6. |
Test the RAM Disk cluster resource.
| a. |
Bring the RAM Disk cluster resource online. |
| b. |
Move the group containing the RAM Disk cluster resource to another
node. |
| c. |
If both these actions are successful, continue with installation.
Otherwise, troubleshoot the problem. |
|
| 7. |
Configure the cluster application to work with the RAM Disk cluster
resource.
| a. |
Make the cluster application dependent on the RAM Disk cluster
resource. |
| b. |
Configure the application to place its temporary data in the folder
which serves as the RAM disk’s mount point. |
| c. |
If necessary, reduce the application’s system memory allocation
limit. |
|
| 8. |
Start the cluster application. |
| 9. |
Test the cluster application with RAM Disk cluster resource.
| a. |
Move the running application to another node. |
| b. |
Restart a node that is available to host the application. After
restarting, move the running application to that node.
|
| c. |
If both these actions are successful, the installation is complete.
Otherwise, troubleshoot the problem. |
|
How
to Remove a RAM Disk from a Cluster |
| 1. |
Stop the cluster application.
| a. |
Remove the cluster application’s dependency on the RAM Disk
cluster resource. |
| b. |
Configure the application to place its temporary data in the appropriate
location. |
| c. |
If necessary, increase the application’s memory allocation
limit. |
|
| 2. |
Delete the RAM Disk cluster resource. |
| 3. |
Uninstall RamDisk or RamDisk Plus on each node. During uninstallation,
any RAM disks present on the node will be destroyed. Also, the RAM Disk
cluster resource type will be unregistered and the corresponding DLLs
deleted. |
| 4. |
Start the cluster application. |
U.S. Patents Nos. 5577226, 5606681, 5918244,
6370615, 6629201, 6651136, 7017013, 7039767, 7111129 and other worldwide patents
pending.
Copyright © 1996-2008 SuperSpeed Software,
Inc. All rights reserved.
