The following guide is written by me on my personal experiences that I have had over the years building and deploying servers. This guide will have the aim of supporting as many users as we can on the server and also have redundancy. Below I will detail each component and what you need to look out for. When you are building servers for a farm (A collection of servers) If possible plan to have one extra server incase you lose a server due to some sort of failure.
Always check on the web if the server has an updated BIOS release and other firmware that you can install. This will help with the smooth running of your server.
Configure The BIOS
First thing to do is turn your server on and go into the BIOS. Disable all of the hardware components that you are not going to use, For example USB devices, Com ports, LPT ports, Sound Devices. Once you have installed the OS configure the boot order (ILP) list to boot to the hard-drive first. This will slightly reduce reboot times and you will also be able to safely reboot the system remotely, What I mean by this is if you reboot the server and there is a floppy disk / CD-ROM in the drive and they are configured as first boot device the system might try to boot to that device.
Hard-Drive : Storage
Always use the fastest disk you can, In a terminal server environment the disks will always be under a lot of pressure, and as a result the life time of the disk will be greatly reduced, So we need to also plan for redundancy. Also make sure you have adequate disk space for the operating system and profiles, Be aware some profiles can be very large in size.
It is best practice to have two hard disks in your server. One used just for the operating system and profiles and the other one for installing all of your programs on such as Microsoft Office, Adobe and so on. This will then help load balance all of the disk activity over the two disks. I would also recommend that you use a USB flash drive for the paging file, But I will cover the paging file later in this document.
It is also a good idea to mirror all of your disks for redundancy. This will cost quite a lot as you need to buy more hard-disks which can be expensive. Also mirroring could possibly slow your disk writing / reading down very slightly as the server needs to read / write to two disks instead of one.
Format the disks with NTFS and not FAT or FAT32. NTFS is faster and also supports setting permissions on files / folders.
Enable disk write caching – Users may experience increased performance if disk write caching is enabled, especially when users log on and off at the same time. Citrix recommends that the cache is set to 50/50 50 read and 50 write.
Personally I don't believe you will benefit from not mirroring disks, if you do all of the above the hard-disks will not be the bottle neck of the system.
To summarise
-Buy the fastest disk you can, SCSI
-Use 2 disks, 1 for the OS + Profiles and 1 for Installing / Running Your Programs
-Make sure you have adequate disk space available
-Mirror your disks for redundancy
-Enable Disk Caching
-Use NTFS file system
Processor
This section is pretty simple and strait forward. Buy the fastest processor you can. If you plan to be installing any operating system newer than Windows NT (IE Windows 2000, Windows 2003) then make sure you buy a processor that can support multi threading. It has been proven that multithreading processors can increase the amount of users you can put onto a server. For more information on hyper threading go to http://www.intel.com/technology/hyperthread/
Make sure your server can support 2 processors. If you install 2 processors then the processing will be spread across the two. Intel Pentium Xeon processors were specially developed for systems with dual processors in.
To summarise
-Buy the fastest processor you can
-Make sure the processor supports multi threading
-Install at least 2 processors into your system
-Buy Pentium Xeon processors or other processor which work well in multi processor systems
Memory
It is very important that your server does not run out of memory. When the server runs out of memory it uses the servers hard-drives page file as memory which then puts extra pressure on the hard-disk to read and write as well as putting extra stress on the processor.
It is very hard to plan how much memory you need, Don't trust anything you read from the Microsoft website, they say you need roughly 20mb per user, this is simply not true. Take a look at my guide here > How Many Users Can I Get On My Server and check the memory section
Also buy memory with the fastest bus speed you can find. You probably will not see a speed increase but the faster the memory runs the better it is for your system.
To Summarise
-Install as much memory as you can
-Use memory with fast bus speed
Network
First of all install at least 2 network cards, Make sure the speed of the cards support 100mb or more. If the network cards are only 10mb then this is to slow. Hard code the network cards speed to prevent the cards from auto-sensing. You will also need to hard code the networks switch as well.
Team the network cards so they act as one (Have one IP address) and also plug each network card into a different switch on the network. This is to add redundancy, if one switch goes down the other one will take over all network processing.
If possible try to have all of the citrix environment servers plugging into the same switch, by this I mean, the citrix servers, Data store and license server.
Air Conditioning / Flow
First of all make sure that the server has a healthy internal air flow. In a terminal server environment all the components are worked hard and as a result can get very hot especially, Processors, Hard-drives, memory. Install as many internal / external fans as you can, This will also help increase the life time of your server.
In my citrix environment we have bought 2 types of servers.
-Compaq Proliant DL360's Generation 1,2 and 3. These servers are very thin, about 1 inch in height and the internal air flow is really bad. It did improve in the generation 2 and 3 models. But in the generation 1 model it only had one fan, and as a result it caused many problems for me over the years.
In my data centre we always have a problem with the air conditioning tripping out (About once every 2 months), When this happens there is always someone around to switch it back on. But the problem is the DL360 servers are the first servers to overheat.
-Compaq Proliant DL380 Generation 2, 3 and 4 servers are what we are buying now to replace the DL360s, The main reason is the internal air flow is so much better than the 360s. The 380 server is much bigger server and can support up to 10 internet fans. I have been using Proliant 380 servers for 2.5 years now and I have not had a single server overheat. So make sure you buy a server which has a good internal air flow system.
The second thing you need to think about is the external environment where the server is going to be hosted. You need to make sure you can keep the room temperature down to a reasonable level. You will need to invest in to some sort of air conditioning / flow system.
To Summarise-Buy a server with good internal air flow system
-Make sure the room temperature is kept down to a reasonable temperature