B
Sizing Guidelines

After determining the number of nodes and servers required, use the information in this appendix to arrive at estimates of your memory and disk requirements.

As a starting point, it is important to note that:

• Each user and resource, whether for a local user or a remote user, takes 2 Kb of disk space.
• An average user needs approximately 2 Mb of disk space per year.
• An active connection requires an average of 750 Kb of virtual memory. Thus, 750 Kb of RAM per connection eliminates any swapping considerations, and no more than 750 Kb of swap space per user is required.

  Note: This figure provided for virtual memory requirements varies according to the operating system.

Memory and disk requirements

To determine memory and disk requirements, the following guidelines should be followed:

Determine the amount of memory required per server. This is calculated by multiplying 750 Kb by the number of connections for that server. If the server will support more than one node, multiply 750 Kb by the number of users for all nodes. Add an additional 64 Mb for system use.

Determine the amount of permanent storage required per server. Each configured user requires approximately 2 Mb of permanent storage. If the server will support more than one node, multiply 2 Mb by the total number of users for all nodes. Add an additional 50 Mb for product files and logs, and also add an appropriate amount for other storage not directly related to the calendar server (i.e. operating system, system swap area, etc.).

Determine the amount of temporary storage required per server. This is calculated by multiplying 750 Kb by the number of logged-on users for the server. If the server will support more than one node, multiply 750 Kb by the number of users for all nodes.

The server has additional system-level storage and memory requirements which are not affected by the number of users. For planning purposes, each server will require 64 Mb of extra memory and 50 Mb of disk space. The disk space requirement is for calendar server software, including logs and executables. These numbers do not include operating system requirements which may vary by vendor.

Determine the number of spindles required per server. One spindle per 100 active users is suggested for both permanent and temporary data. In other words, to support 100 users, one spindle for permanent data and one spindle for temporary data is recommended. This is a performance-related requirement to ensure that disk I/O is distributed across multiple drives. For optimal performance, three additional drives should be provided: one for the operating system, one for the operating system swap space, and one for the server executables and logs.

The number of spindles for permanent and temporary storage has been established based on the recommendation that one spindle be used for each 100 active users for permanent data, and one spindle for each 100 active users for temporary data. A number higher than 100 may be used, with some degradation in performance; the higher the number of active users per spindle, the greater the performance degradation.

Finally, the size of the disks for permanent and temporary storage may be identified. For each server (or for each node if separate drives will be used for each node), divide the total disk requirements by the number of spindles.