5.1.4 Simple Sizing Exercise for Calendar Server 6.3 Storage Requirements

This section describes a simple sizing method using a few rough formulas based on a medium usage profile. They allow you to figure out how many front-end and back-end servers you need and how much storage.

This sections covers the following topics:

• 5.1.4.1 Definition of Medium Usage Profile for a Calendar Server 6.3 Deployment

• 5.1.4.2 Number of Front-End CPU's

• 5.1.4.3 Number of Back-End CPU's

• 5.1.4.4 Amount of Storage Needed

5.1.4.1 Definition of Medium Usage Profile for a Calendar Server 6.3 Deployment

For our rough estimates, we are assuming the following:

• All clients are Web clients.

  Therefore, the only inputs to be used are: total number of users, and percent concurrency.

• The average size calendar event size is 5K.

• Each person creates ten events or todos per week.

• 80% CPU utilization.

• 900 MHz CPU's.

• 1 GB RAM per CPU.

• Two years' worth of calendar data stored on system.

• Six hot backup copies held in storage.

5.1.4.2 Number of Front-End CPU's

The formula is:

Number of CPU's = Number of Concurrent Users divided by 4800

5.1.4.3 Number of Back-End CPU's

The formula is:

Number of CPU's = 4 CPU's per 500,000 configured users

5.1.4.4 Amount of Storage Needed

The formula is:

Amount of Storage Per User = 100 emails per week, multiplied by 52 weeks a year, multiplied by 5K per email, multiplied by the number of years worth of data to keep online, multiplied by the number of copies (5 backups + 1 working copy) kept online = 100*52*5K*2*(5+1) = 65 MB storage per user.

That is 2.6 MB per user per year per copy held online.

The final number depends on how many hot backups or archival backups you keep online. For this example, 5 backup copies was the number used.