Free Support Guide
How to Choose a Server
Once a network has grown beyond 5 users a workgroup environment becomes unreliable for transferring information
and accessing resources over the network. At 10 users you can expect to see several computers crashing a week
(unexpected errors). The risk to your hard earned data increases. When this happens, typical problems are file
corruption, and worst still the operating system corrupts even the newer operating system have these problems. Also
newer Operating Systems have connection count limit built in, often resulting in unexplained file Access Denied errors.
At this point you need a server.
This server may still be used in a workgroup environment. A server being used in a workgroup is often referred to as a
Workgroup Master. This machine will eliminate your connection limit issues providing you have enough user licenses to
access the machine and you have moved the shared resource to this machine. You will also benefit from the fact that
this type of machine is left on so it resources are available to all the users. This will allow users to turn their own
machines off and perform updates as and when needed without affecting other users. You can also if careful make sure
this machine is the network “MASTER BROWSER” thus preventing forced election of all the computers on the network.
By using the server as a domain master you will gain many more benefits, centralised security being the most important.
On a network these systems are responsible for providing secure access to network resources. A typical Microsoft
windows server will provide the following services.




DHCP – Assigns IP Addresses to requesting devices.
DNS – Provide name services to all network equipment
ADS – Active Directory Services for requesting Microsoft Windows Users and Services
Common authentication to server services
Whichever mode you choose to run these machines in the following statements about the hardware will apply and you
should consider all points when making your choice.
These machines are designed to be more reliable than the average desktop machine:





They work a lot harder
They are rarely turned off
The drives are normally in constant use
They are often under constant attack from remote communication sources
Their designed operational life tends to be longer than that of a desktop computer
There are 3 parts to the decision process when choosing a server.



Network Resource Planning
Server Hardware choices
Server Software Choices
Guide Reference: FSG-0002-01
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How to Choose a Server
Network Resource Planning
In this section we use a few technical terms which are explained more fully under the Server Hardware Choices section.
This comes down to how many users, what resources are being provided, and how many branch offices (remote sites)
or remote users need access.
Consideration should be given to branch offices having their own network and local server this helps security by keeping
local resources local to the users as well as preventing un-necessary network traffic across the data communication link
(Often the internet). (If you are running an application service for large number of external/home workers you may
need to increase the power of the server and even consider some fault tolerant technology.
As the number of users grows you should add more servers to the network. Use the following as a guide for the number
of servers at each site:
Number of Users
Up to 30 Users
Up to 60 Users
60 Users and Over
Server
Server 1
Server 1
Server 2
Server 1
Server 2
Server 3
Function
Primary Master
Primary Master
Secondary Master
Primary Master
Secondary Master
Secondary Master
Services
DHCP, DNS, ADS, GC
DHCP, DNS, (ADS), (GC)
(DHCP), (DNS), ADS, GC
DHCP, GC, (ADS)
(DHCP), DNS, (GC)
ADS, (DHCP)
The above services are the basic network provision services for a Microsoft Server based solution a Linux/Unix solution
will have equivalent based services. The services in parenthesises are backup services which should provide a degree of
fault tolerance. Also many IT professionals have different ideas about the splitting of these services and often your
operating environment may determine how these services are distributed. What we are trying to show is that the
services are distributed evenly amongst the servers.
Once your user count goes beyond 90 users performance improvement is not necessarily achieved by adding extra
servers. To achieve better performance it may be better to provide higher performance servers. This is because services
generally can’t be split across 2 or more servers unless you are using a clustering technology.
Also if you operate your own email server and have branch offices with more than 10 users you would benefit from an
additional mail server at these sites.
With a more recent development of Off-Premise server services your choice widens. You could reduce the number of
servers you require by out sourcing some of your server based services. Read our Free Support Guide FSG-0001-01 for
more information.
One of the prime functions of a server is to provide file storage either for an application or directly for users. Choosing
the right storage strategy is very important. So here will provide some guidance on storage capacity, and in the Server
Hardware Choices section you will find information on the type of storage systems & devices.
Storage Capacity Requirements
The storage capacity you need depends on several factors; the applications you use; number of users; the amount of
document processed and stored; expected business growth; historical archive period. Always over estimate the figure
and always round up. Remember your server is expected to last 5 years data growth.
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Guide Reference: FSG-0002-01
How to Choose a Server
The figures given below are for guidance and you need to make your own assessment to gain an accurate storage
capacity figure for the business. Getting the storage strategy wrong or the storage capacity figure wrong could involve a
serious amount of down time getting the storage strategy technology right will mean very little down time.
Storage Capacity Guidance Table for 5 years.
User Type
Activity
Light Commercial User
Email
Documents
Document Scans (Pages)
Medium Commercial User
Email
Documents
Presentations
Document Scans (Pages)
Heavy Commercial User
Email
Documents
Presentations
Databases
Document Scans (Pages)
Document Clerk
Email
Document Scans (Pages)
Application User (No Email)
Application
Application User with Email
Email
Application
File Count
Per Week
25/50
25
5
Totals:
50/100
50
0.5
25
Totals:
100/200
50
1
0.25
50
Totals:
100/100
500
Totals:
n/a
Totals:
100/100
n/a
Totals:
Capacity Required
6 Months
1 Year
60MB
120MB
1MB
2MB
65MB
130MB
126MB
252MB
120MB
240MB
2MB
4MB
130MB
260MB
325MB
650MB
577MB
1.154GB
240MB
480MB
2MB
4MB
260MB
520MB
325MB
650MB
650MB
1.3GB
1.477GB
2.254GB
156MB
312MB
6.5GB
13GB
6.656GB
13.32GB
50MB
100MB
50MB
100MB
156MB
312MB
50MB
100MB
206MB
412MB
2 Years
240MB
4MB
260MB
504MB
480MB
8MB
520MB
1.3GB
2.308GB
960MB
8MB
1.04GB
520MB
2.6GB
5.908GB
624MB
26GB
26.63GB
200MB
200MB
624MB
200MB
824MB
3 Years
360MB
6MB
390MB
756MB
720MB
12MB
780MB
1.95GB
3.462GB
1.44GB
12MB
1.56GB
780MB
3.9GB
8.862GB
936MB
39GB
39.94GB
300MB
300MB
936MB
300MB
1.236GB
No Archive
600MB
10MB
650MB
1.26GB
1.2GB
20MB
1.3GB
3.25GB
5.77GB
2.4GB
20MB
2.6GB
1.3GB
6.5GB
14.77GB
1.56GB
65GB
66.56GB
500MB
500MB
1.56GB
500MB
2.06GB
For other Professional Users add the following to a Medium Commercial User to arrive at their Storage capacity.
CAD/CAM User
CAD/CAM Drawings
5
650MB
1.3GB
2.6GB
3.9GB
6.5GB
Web Designer
Web Pages
100
130MB
260MB
520MB
780MB
1.3GB
Graphic Designer
Graphic Design
10
2.6GB
5.2GB
10.4GB
15.6GB
26GB
Photographer
Photos (Hi-Res) 10MB
250
65GB
130GB
260GB
390GB
650GB
Photographer
Photos (Med-Res) 5MB
250
32.5GB
65GB
130GB
195GB
325GB
Photographer
Photos (Lo-Res) 1MB
250
6.5GB
13GB
26GB
39GB
65GB
Photographer
Photos (Web) 100KB
250
650MB
1.3GB
2.6GB
3.9GB
6.5GB
Please note that this is a guide most businesses will have differing requirements.
In addition to the above every server will require additional storage space for the operating system, security application,
applications they serve to users and a cache storage area normally 2-3 times the RAM size of the server.
From the above table a couple of things become very clear, email, scanned documents and graphics consume storage
capacity. Without an archive strategy the numbers become very large indeed.
Guide Reference: FSG-0002-01
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How to Choose a Server
How to use the guide
Make a list of all your user types and the number of users of that type. Do this for all your sites. Remember to add your
remote users to the list. (Only relevant for Email and Application Services)
Add up all the users add to this the expected number of users you think you may have in 5 years time. This will tell you
how many servers you need to operate the basic services. You may need to add an extra server for an application you
may be running. Write a list of these servers down.
Any Off-Premise server service you subscribe to you can omit the server and its storage requirements.
Next decide how much archive history to keep on the server. You could even keep a different archive history for emails
from the main file storage. You could keep 1 year email history and 5 years of files.
On your list of user types write down the total storage capacity for that user type required minus the email capacity (use
the figure that is in the same archive history column you have chosen for the main file storage) and multiplied this by
the number of user of that type. Do this for all your user types but ignore the application user types.
On your list of user types write down the email storage capacity for that user type for your desired archive history
option. Do this for all the user types.
If you have application user types (you should have one for each application type) use the total number users multiplied
by the storage required. Better still is to a figure given to you by the application vendor this may be a size per user or
size based on the number of records. Use the most appropriate figure and remember you have to think about what the
size will be in 5 years time. Also don’t forget to add the application installation requirements too. Alternatively divide
the number of records you have with the file size (or directory size of the application data) this will give you a record
size multiply this by the number of records you hope to have in the application after 5 years add 20% to the figure for a
safety margin.
Now total all the mail file storage and email storage capacities from the user types. Hopefully now you should have a
total storage requirement for main file storage, emails, and each application.
Now for each server add 30Gbytes plus 3 times the RAM capacity and 50MB multiplied by the number of total network
access users.
Example:
This company has 22 Staff at 2 sites and also has 3 remote staff. They want to have their own internal email server,
accounts system and CRM system. The 3 remote users connect to site 1. This company has no archive policy for File
usage and a 2 year archive policy for emails.
First thing is to identify the types of staff.
4 staff are Light Commercial Users
4 staff are Medium Commercial Users
2 staff are Heavy Commercial Users
10 staff are Application with email users
2 staff are Graphic Designers
3 staff are CAD/CAM Users
Page 4 of 14
Guide Reference: FSG-0002-01
How to Choose a Server
The next step is to work out the number of users for each application. This is an important step so you know the number
of access licenses required for applications.
25 Network Access Users (Total number of staff)
8 Accounts System Users
9 Users on our CRM System (3 are Remote Users)
25 Users using Email
Next draw up a list of users and the application user count at each site and add the remote users to the site they
connect to.
Site 1:
12 Staff are based at this site
1 Heavy Commercial User
2 Medium Commercial Users
3 Light Commercial Users
6 Application with email users (3 Users are Remote)
1 Graphic Designer
2 CAD/CAM Users
Number of users for each application
15 Network Access Users (3 are Remote)
6 Users use Accounts System
6 Users use the CRM System (3 are Remote)
15 Users using Email (3 are Remote)
Site 2:
This site has 10 Staff
1 Heavy Commercial User
2 Medium Commercial Users
1 Light Commercial Users
4 Application with email Users
1 Graphic Designer
1 CAD/CAM Users
Number of users for each application
10 Network Access Staff
3 Users use Accounts System
3 Users use the CRM System
Now we have the users count and types and the split between the locations we can put together a server count and a
storage capacity estimate.
If there was a high speed dedicated communication link between the 2 sites we could use 4 servers but we will assume
there is not a dedicated high speed communication link.
Guide Reference: FSG-0002-01
Page 5 of 14
How to Choose a Server
As the user count is over 5 at each site it would be better to use 2 servers one at each site. In addition we have over 10
users at each site using email so we would require 2 mail servers to handle the email. Also 2 additional servers would be
required to handle the 2 main applications.
For an On-Premise solution we would require 6 servers, 4 at site 1 and 2 at site 2. At the end of this example we will give
you an alternative solution using a Hybrid solution using On-Premise and Off-Premise services.
Now we need calculate the storage capacity required.
Site 1:
1 Heavy Commercial User
2 Medium Commercial Users
3 Light Commercial Users
6 Application with email users
1 Graphic Designer
2 CAD/CAM Users
User Count
User Type
1
2
3
6
1
2
Heavy Commercial User
Medium Commercial Users
Light Commercial Users
Application Users with email
Graphic Designer User
CAD/CAM User
Main File Storage
12.37GB
9.12GB
1.98GB
30.57GB
22.14GB
Totals: 76.18GB
Email Storage
4.136GB
960MB
720MB
3.744GB
480MB
960MB
11GB
Site 2:
1 Heavy Commercial User
2 Medium Commercial Users
1 Light Commercial Users
4 Application with email users
1 Graphic Designer
1 CAD/CAM Users
User Count
User Type
1
2
1
4
1
1
Heavy Commercial User
Medium Commercial Users
Light Commercial Users
Application Users with email
Graphic Designer User
CAD/CAM User
Main File Storage
12.37GB
9.12GB
660MB
30.57GB
11.07GB
Totals: 63.79GB
Email Storage
4.136GB
960MB
240MB
2.496GB
480MB
480MB
8.792GB
Now we have the storage requirements for the user’s files and emails. The email application program requires 10GBytes
of installation and operating space
The accounts application vendor told this company that 100Mbytes of storage per user per year was more than
adequate for the expected accounting usage.
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Guide Reference: FSG-0002-01
How to Choose a Server
As there are 8 Accounting users 4GBytes of data storage is required. The application requires a further 1.5Gbytes on
installation space.
The companies CRM System is based on a SQL database they have 1,000 records stored taking 160Mbytes of space they
think they going grow their CRM records to 13,000 over the next 5 Years.
1,000 Records / 160Mbytes = 160Kbytes per Record
13,000 Records x 160Kbytes = 2.08GBytes of storage required over 5 years
The CRM application needs only 35Mbytes of installation space.
Now we calculate what each server requires. For this example all the servers have 16GBytes of RAM the RAM
requirements for a server are discussed later in the section about server hardware.
Server
Site 1 - Primary Master
Requirement
Operating System
25 Users x 50Mbytes
Main File Storage
Cache RAM 16Gbytes * 2
Site 1 – Email Server
Operating System
25 Users x 50Mbytes
Email Storage
Email Application Space
Cache RAM 16Gbytes * 2
Site 1 – Accounts Application Server
Operating System
25 Users x 50Mbytes
Application Data Storage
Application Space
Cache RAM 16Gbytes * 2
Site 1 – CRM Application Server
Operating System
25 Users x 50Mbytes
Application Data Storage
Application Space
Cache RAM 16Gbytes * 2
Site 2 - Primary Master
Operating System
25 Users x 50Mbytes
Main File Storage
Cache RAM 16Gbytes * 2
Site 2 – Email Server
Operating System
25 Users x 50Mbytes
Email Storage
Email Application Space
Cache RAM 16Gbytes * 2
Total:
Total:
Total:
Total:
Total:
Total:
Guide Reference: FSG-0002-01
Capacity
30GBytes
1.25Gbytes
76.18GBytes
32GBytes
139.43GBytes
30GBytes
1.25Gbytes
11GBytes+ (8.792GBytes)
10GBytes
32GBytes
93.042GBytes
30GBytes
1.25Gbytes
4GBytes
1.5GBytes
32GBytes
68.75GBytes
30GBytes
1.25Gbytes
2.08GBytes
35MBytes
32GBytes
65.365GBytes
30GBytes
1.25GBytes
63.79GBytes
32GBytes
127.04GBytes
30GBytes
1.25Gbytes
8.792GBytes + (11GBytes)
10GBytes
32GBytes
93.042GBytes
Page 7 of 14
How to Choose a Server
Operating a single domain will require the total user count requirement for network access services and with 2 email
servers using the total email storage figure.
Alternative Hybrid Solutions
All the following 7 solutions are valid and will work but they don’t fulfil the company’s requirements. The company
wanted keep the applications On-Premise. All the following options have a cloud based element.
Hybrid Solution 1
Server Solution
Site 1 - Primary Master
Off-Premise Email Service for 25 Users
Off-Premise Accounts Application Service 8 Users
Off-Premise CRM Service for 7 Users
Site 2 - Primary Master
Solution requires 2 Servers and 3 Off-Premise Services
Capacity
139.43GBytes
n/a
n/a
n/a
127.04GBytes
Hybrid Solution 2
Server Solution
Site 1 - Primary Master
Off-Premise Email Service for 25 Users
Site 1 - Accounts Application Server
Off-Premise CRM Service for 7 Users
Site 2 - Primary Master
Solution requires 3 Servers and 2 Off-Premise Services
Capacity
139.43GBytes
n/a
68.75GBytes
n/a
127.04GBytes
Hybrid Solution 3
Server Solution
Site 1 - Primary Master
Off-Premise Email Service for 25 Users
Off-Premise Accounts Application Service 8 Users
Site 1 - CRM Application Server
Site 2 - Primary Master
Solution requires 3 Servers and 2 Off-Premise Services
Capacity
139.43GBytes
n/a
n/a
65.365GBytes
127.04GBytes
Hybrid Solution 4
Server Solution
Site 1 - Primary Master
Site 1 - Email Server
Off-Premise Accounts Application Service 8 Users
Off-Premise CRM Service for 7 Users
Site 2 - Primary Master
Site 2 - Email Server
Solution requires 4 Servers and 2 Off-Premise Services
Page 8 of 14
Capacity
139.43GBytes
93.042GBytes
n/a
n/a
127.04GBytes
93.042GBytes
Guide Reference: FSG-0002-01
How to Choose a Server
Hybrid Solution 5
Server Solution
Site 1 - Primary Master
Off-Premise Email Service for 25 Users
Site 1 - Accounts Application Server
Site 1 - CRM Application Server
Site 2 - Primary Master
Solution requires 4 Servers and 1 Off-Premise Services
Capacity
139.43GBytes
n/a
68.75GBytes
65.365GBytes
127.04GBytes
Hybrid Solution 6
Server Solution
Site 1 - Primary Master
Site 1 - Email Server
Site 1 - Accounts Application Server
Off-Premise CRM Service for 7 Users
Site 2 - Primary Master
Site 2 - Email Server
Solution requires 5 Servers and 1 Off-Premise Services
Capacity
139.43GBytes
93.042GBytes
68.75GBytes
n/a
127.04GBytes
93.042GBytes
Hybrid Solution 7
Server Solution
Site 1 - Primary Master
Site 1 - Email Server
Off-Premise Accounts Application Service 8 Users
Site 1 - CRM Application Server
Site 2 - Primary Master
Site 2 - Email Server
Solution requires 5 Servers and 1 Off-Premise Services
Capacity
139.43GBytes
93.042GBytes
n/a
65.365GBytes
127.04GBytes
93.042GBytes
Main file storage capacity is generally stored on the Primary Master server but can be stored on any of the servers. It is
also possible to store these files separately on dedicated storage devices that attach to the network such as a Storage
Area Network (SAN) or a Network Attached Storage (NAS). These technologies are discussed in a separate document.
When you use such technologies you can subtract the Main File Storage, Email Storage or Application Storage capacity
from the server requirement and add the appropriate figure your storage capacity requirement to your dedicated
storage device.
Backup Planning
Once you have compiled this information for your network you can also derive the amount of capacity required for your
backup system. To this add the capacities of all the servers used & dedicated storage devices located at each site, this
will give you the backup capacity required for each site. The backup device generally is attached to only one of the
servers at each site.
Using the above example the backup capacity requirement for each site would be:
Site
Backup Capacity
Site 1
Site 2
367GBytes
221GBytes
Guide Reference: FSG-0002-01
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How to Choose a Server
Various backup strategies can be adopted for the needs of this company. The backup may be split into smaller chunks
but your backup device capacity should be greater than the largest Logical storage device you have at the site.
Other considerations about network resource planning
You should have an Uninterruptable Power Supply (UPS) of the adequate power rating for every PSU Mains connection
on the server with the most mains connections. One UPS may serve more than one server but not 2 PSU’s on a single
server. This will prevent corruption of files and the operating system if power is suddenly lost.
When considering the cost remember the most expensive item on your network is the user. If they can’t work when a
server is down it is still costing you their wages.
Hardware Server Choices
Now you have planned the network infra structure you can make a more informed choice on the hardware technologies
deployed in a server system. Servers are in their basic form the same as desktop computers they will function the same
way. You could use a desktop computer with a server operating system. So why are server products different?
Server main boards are built to last longer
Most servers have a dual redundant power supply
Server RAM memory normally has Error Correcting Code (ECC)
Interface Cards should be Active rather than Passive (Have on-board CPU’s)
Main boards
Server main boards are designed to be more reliable. In general they support multiple CPU’s, use ECC Reg. Memory and
have other feature. They support 64Bit Cards which allow data to move faster to peripherals and storage devices. For
this reason High Performance workstations sometimes use server main boards and the technologies discussed below.
Redundant Power Supply
This means that there are extra power supply units which are active in case one fails. This will allow the server to
continue operating. When using Redundant Power Supplies it is important make sure that if a unit fails the remaining
power supply(ies) are able to provide the required power rating. If this is not done when a PSU fails it will cause a chain
failure to occur on all the remaining units due to excessive power draw. There is a double benefit to Redundant Power
Supplies in normal operation all the PSU’s will share required power load between them making them less stressed thus
more likely not to fail as well as the fact that you system should continue to operate if you have a failure of a single unit.
ECC Reg. Memory
This means that every byte of information is stored with an error correction bit so when an error is detected it can be
corrected. The register means that the memory will hold the data so that it is available through the processor
instruction cycle this improves the speed at which the CPU can obtain the stored data from the RAM and make it more
reliable. Although memory access errors are rare something in the order of 1.0E 18, they will nearly always cause the
server to crash.
Storage Devices
SAS/SCSI v SATA/IDE Hard Disk Drives
A SAS (Serial Attached SCSI (Small Computer System Interface))/SCSI based server will offer better performance and
more reliable than SATA (Serial Advance Technology Attachment)/IDE (Integrated Drive Electronics) storage devices.
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Guide Reference: FSG-0002-01
How to Choose a Server
SATA/IDE drives should only be used on the Low End Servers as an economic option. SAS/SCSI disk drives are by far the
best devices they are reliable and very fast. In general most servers use a SAS/SCSI chassis which facilitates hot
swapping features to allow a failed drive to be replaced while the server is up and running you can only do this if you are
using a relevant RAID configuration.
The most important factor for any type of Hard Disk Drive (HDD) is its spin speed. This determines how fast data can be
pulled from the magnetic stored information on the platter to the controller. The next important factor for speed is the
head time given as track-to-track and head settling time.
SATA/IDE drives 7,200rpm is better than 5400rpm
SAS/SCSI 15,000rpm is better than 10,000rpm
RAID Technology
RAID stands for Redundant Array of Inexpensive Disks. We will ignore the inexpensive part because server disk drives
are normally more expensive than desktop drives for the reasons stated. But when this term was coined drives in use
where either desktop hard drives or mainframe hard drives. What is of our concern is the fact that a group of disk
drives are available to controller. This controller is more intelligent than a standard disk drive interface and will treat
these separate drives as part of a storage unit depending on the configuration that it has been given. RAID controllers
are very intelligent interfaces.
RAID configurations are defined by a number and are referred to universally across the industry. There are 3
configurations of interest:
RAID0
All the Drives are used to create a single volume this improves access speed as there are more drive heads to access the
data stored on the volume. There is no security of data in this configuration.
RAID1
2 drives are used; one is used as an exact match to the other this configuration is often referred to as a Mirror Array.
This configuration is slower to write data as it has to write the data twice, but is the most secure as one drive can fail
and the server will still continue to operate normally.
RAID5
3 or more drives are used to create a volume with 3 drives, 2 drives make the volume while the 3 rd is a parity drive. This
configuration is a compromise between speed and security. If a drive fails the server will have to be taken offline to
repair the array but should continue to work, it will access data faster than RAID1 as there is more heads across the
volume but will write slower as the parity drive requires calculating as well as writing.
There are other RAID configurations that are not commonly used and there are few adopted configurations that are.
RAID 1+0/RAID 0+1/RAID10 - RAID0 then mirrored RAID1
RAID 5+0/RAID 0+5/RAID50 - RAID0 made of RAID5’s
RAID 5+1/RAID 1+5/RAID51 - RAID5 then mirrored RAID1
HOT SPARE
This is a name given to a drive that is in the array and is available to take over and be used if a drive should fail in an
array. Most intelligent RAID controllers will do this automatically.
Guide Reference: FSG-0002-01
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How to Choose a Server
Do not think that a RAID is a replacement for backing up they are intended as a means to keep the server up and
running or providing larger storage capacities. If your server is destroyed by Fire, Flood, Explosion etc, it will result in the
loss of all your data.
Given the cost of drives you should always operate with one of the RAID configurations and preferably with a HOT
SPARE available for each array.
You should purchase a drive chassis is it will allow for swapping of disk drives when a drive fails.
High Performance
Standard Servers come with 1-2 Processors and embedded RAID controller they are designed as a complete solution for
a smaller company often including a backup drive. High Performance Servers offers many additional features and a
greater range of options.
2 or more processors with many cores
SAS/SCSI RAID controller
Significant RAM expansion capability
Drive Chassis
Virtualisation
Virtualisation is when you run separate instance of the operating system on the same hardware platform. This means
that you could have 4 servers appearing on the network but in fact there is only one physical server system. Most new
main boards support the capability of virtualisation. When you virtualise a system the operating system that manages
the virtual machines is called the Host and the virtual machines it is running are referred to as the Guests.
Fault Tolerance Technology
When the term Fault Tolerant Technology is used it means there is duplication in the hardware that can take over if a
fault occurs normally without causing any disruption in service. The 2 most common of these technologies we have
discussed earlier is the Redundant Power Supply and some RAID configurations (RAID1, RAID5). These 2 fault tolerant
technologies cover the most stressed components in a computer system. Another fault tolerant technology found in
some high performance rack servers is a group of hot swappable fans. To make a server fully fault tolerant is extremely
costly as special network core switching technology is required. Clustering technology becomes a better alternative
when you need to achieve this.
Clustering Technology
Clustering technology is when multiple servers are linked together to provide what will appear as a single server. This
sounds easy but in practice requires specialist hardware and software. This technology is used when you have100’s or
even 1000’s of users. Internet hosting companies and Internet service providers use this type of technology extensively.
The additional benefit of this technology is that it is fully fault tolerant when implemented correctly. A server machine
may fail totally and the services it provides will continue to be available as they were shared amongst several servers. In
reality all that happens that the work load is such spread across fewer servers. Hardware vendors introduced the term
blade servers. These are bare bone server boards in compact form that slide into to a rack that provides a common bus
for these servers to talk to each other and the peripherals that connect to this server. This makes a cluster server more
cost effective and saves a space and power.
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Guide Reference: FSG-0002-01
How to Choose a Server
Server Software Choices
The Network Operating System (NOS) is just as important as the server hardware. There are 2 main operating system
types UNIX/LINUX & Microsoft Windows, the only exception to these are generally vertically market application servers
that serve the application to users via terminal or user computer using a thin client application.
UNIX/LINUX
Mainly used by larger companies with custom written applications or Internet Service Providers/Hosting. Although the
software costs are very low the support required to maintain these systems is significant (Not problem to companies
that employ lots of technical staff with the required skills.
Microsoft Windows
Tends to be used commercially integrates well to client systems. It also offers a familiar interface for doing tasks on a
server so the support level required is much lower. Microsoft offers many versions of its server products and each
version has its own set of restrictions. For smaller companies Microsoft offer server products with fixed number of user
access licenses (Commonly referred to as CALs) once you reach this limit you have to upgrade your server operating
system to the next level.
Microsoft Licenses are based on the number of processors or the virtualisation environment needed these Licenses
require CAL licenses for each user.
In both cases additional Server Service Application like email or SQL will require their own CAL Licenses for the number
of users using the particular service.
In the late 1990’s Microsoft introduced a product for small businesses to use. This product was designed to run on a
single server and was limited to the number of users that could be connected. This product offered great value to small
businesses particularly as the price of hardware began to fall in the early 2000’s. The key attraction of this product was
Microsoft Exchange Server was included which meant the 2 most important components of an IT strategy where
bundled together.
Microsoft in 2012 announced there will be no inclusion of the Microsoft Exchange Server in this product. ‘Microsoft
Windows Small Business Server 2011’ being the last release with the email server product and to make matters worse
this product was based on ‘Microsoft Windows Server 2008 R2’ which means the support cycle is reaching the end.
This product was an extremely popular choice for companies that wanted on-premise server technologies. The absence
of this product will make the choice for many small businesses even harder. Microsoft’s reasoning is that no one is
buying licenses for product they don’t wish to use as a company may wish to use a cloud based service for their email.
It would also be fair to say with recent explosion in email usage user’s mailboxes have grown significantly and having a
mail server and a primary domain master service on a single server does not perform well.
In the above example you could operate using Essential Business Server 2012 but there is no expansion capability for
new users. It would be more prudent to opt for Standard Server 2012 which will allow for more than 25 Users, You will
also get the benefit of being able to isolate the main function of the server into their own virtual server. This will make
support and migration as you grow easier.
There is an alternative to solution to our example and that is to virtualise all the servers into a physical hardware
platform. This solution would require:
Guide Reference: FSG-0002-01
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How to Choose a Server
2 High Performance servers one at each site
1 Data Centre Server 2012 License for Site 1
1 Standard Server 2012 License at Site 2
Be aware that the storage requirements change as does the operating amount of memory.
Summing Up
In general when deciding on your server needs use the following points to determine your best hardware and software.
Buy the best you can afford
The Storage requirement always grows over time. If you are not sure of your storage growth use a
storage option that allows you to expand your storage later. (A chassis with some empty drives spaces.)
A Second CPU can normally be added later but generally it is a minor cost in the overall scheme of
things.
Remember you are planning for 5 years growth.
Make sure your chosen Server operating systems will allow for your expected user growth.
When calculating the cost divide the total cost by the number of users, this figure tends to give you a
different perspective on the cost.
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Guide Reference: FSG-0002-01