25 August 1998

A Technique for Calculating Computer/User Administrative Support Requirements

Douglas Mitchell


In two of the organizations I have supported, growth in these organizations caused systems administrative support requirements to grow as well, past that which I could perform working alone. In my current position, I have taken this state of affairs as an opportunity, to demonstrate to management systems support needs. To do this, I developed the following technique to calculate the number of hours of support effort required by all hardware and software on the network I support.

Hours by Type Total = Hours Type + Hours Instance * Number Instances

This relationship takes into account both the effort required when any new type of hardware or software is acquired (Hours Type) and the effort required to maintain the average instance of that hardware or software(Hours Instance). To determine the Hours Type constant calculate the hours required for an administrator to learn and to stay current on hardware or software of this type. The Hours Instance includes the number of hours of support the average user requires, and the time to support each instance of this hardware or software. Calculating the total number of hours of support effort for the network is then just a matter of adding all the various Hours by Type Total quantities.

Hours Total = å Hours by Type 1 Total + Hours by Type 2 Total …Hours by Type n Total

Using these equations in a spreadsheet, the Hours Total quantity for your entire network support effort may be determined from the Hours Type and Hours Instance constants.

An Example:

Disclaimer: The numbers used in this example while consistent and reasonable may differ significantly from support requirements by your users and systems.

Let us suppose we need to support a network of computers:10 MS Windows 95, 15 NT Workstation and 2 NT Server installations. The MS Windows 95 and NT Workstations computers use the same hardware configuration while the NT Server installations contain multi-processor motherboards and RAID hardware. The users on all systems will be using MS Office as their primary application.

The Windows 95 and NT Workstation computer hardware require the same amount of support since the hardware is consistent. Let us say that the hardware of these machines require 4 days of effort per year for an administrator to stay current on the particular type of motherboard, processor, hardware, bios, etc. Each instance of these computers requires another 2 days of effort per year for common hardware repairs.

95/NT Hardware Hours Year = 32 Hours + 25 Instances * 16 Hours = 400 Hours Year

The servers being based on a different motherboards and disk I/O hardware require another 5 days of support for study per year for their type of hardware and because of the high availability requirements of these systems also each require another 5 days of support for general hardware repairs. (Replacement of failed hard drives in RAID arrays – rebuilds, tape library maintenance, etc) The total amount of support time for hardware of the computers on our network is then:

NT Server Hardware Hours Year = 40 Hours + 2 Instances * 40 Hours = 120 Hours Year

Total Hardware Hours Year = 400 + 120 = 520 Hours Year .

The above calculations allow for the hardware support to our systems. Now we may calculate the support required for maintenance to the operating systems. Let us say that to stay current on Windows 95 requires 5 days of study a year. Windows 95 users generally are less experienced, so that they and their installations will require 4 days of support each.

95 O/S Hours Year = 40 Hours +10 Installations/Users * 32 Hours = 360 Hours Year

The NT operating system requires the same 5 days of study for administrators to stay current but since these users are more experienced and independent we will only allow for 2 days of user and installation support.

NT O/S Hours Year = 40 Hours + 15 Installations/Users * 16 Hours = 280 Hours Year

The NT Server operating system also requires an additional 5 days of study, and upkeep, user account maintenance, permissions on files-systems, backups, mirroring of system/boot drives, etc. require 10 days of support each.

NT Server O/S Hours Year = 40 Hours + 2 Installations * 80 Hours = 200 Hours Year

Total O/S Hours Year = 360 + 280 + 200 = 840 Hours Year .

As MS Office is a fairly complex set of programs, at least 5 days per year are required for an administrator to stay current on this software. Additionally, our 25 users will need at least 3 days of support each for themselves and their installations.

MS Office Hours Year = 40 Hours + 25 Installations/Users * 24 Hours = 640 Hours Year

The total number of support hours required by our hardware, operating systems, and Office productivity tools is:

Total Support Hours Year = 520 + 840 + 640 = 2000 Hours Year .

As 2000 Hours per year is roughly one person equivalent, then one administrator is required to support our example network.

Once the Hours Type, and Hours Instance constants for hours/year or hours/month are calculated, a manager can not only determine current staffing needs, but can predict staffing requirements for future hardware and software purchases. I have found that this technique allows me to better communicate support needs to my management. I have used it to estimate what hardware and software will be neglected due to lack of support, and have also post-dicted support and maintenance problems given available effort and existing systems. (What better way to test the Hours Type and Hours Instance constants than by post-dicting your support difficulties of the past month?)

With support broken down in this way I have been able engage my management to consider the assumptions on which the calculations are based. When your Directors are aware that 3 person-months of effort are required to implement some new Gee-Wiz technology and continued support will be 1 person-month per year equivalent thereafter, you can ask for the personnel to implement at the outset. You are also in a position to describe why support maintenance is falling behind due to insufficient staffing, because required support hours can be determined. The continued cost of maintaining obsolete systems can be demonstrated. This technique, through the way it breaks out hidden support costs, has lead to a complete reorganization of systems support tasking in my current organization.


Douglas Mitchell is the Systems Manager for the CLAIRVOYANCE Corporation, where he maintains C++ development environments on a mix of MS NT and UNIX computers. Mr. Mitchell received his B.Sc. in Electrical Engineering at the University of Akron. Since earning his degree he has worked as a Software Engineer, Systems Administrator, and later Systems Manager. He may be contacted at d.mitchell@ieee.org.