When we talk of protecting data on servers, we are referring to prevention of unauthorized access to the data, preventing the data from being corrupted or destroyed as well as preventing the common virus attacks. The threat to data can be accidental or intentional and so a number of measures need to be taken. Here are some that must be ensured.
Physical protection of servers
Since the data is stored on the servers, it is important that the servers are kept physically safe so that there is no unauthorized access to them. This means that the server room should be locked at all times within a secured building with only authorized personnel having access to these rooms that way the data cannot be stolen or corrupted through physical access to the servers.
Physical protection also involves avoiding risks of damage to the servers, the server room needs to be dry and cool to keep the servers running well. Usually this will require the use of air conditioning. You would also need to ensure that support staff like cleaners understand that the servers are delicate and should not be wet, or allowed to heat up. In general, do all that is possible to see to it that the servers are safe from theft and damage.
It should go without saying that the data should be password protected and only authorized individuals should have access to these passwords. It is not enough though to just have passwords, the passwords need to be changed periodically so that if some unauthorized persons may have gotten the password, the threat to the data will be reduced with change of password.
There is a combination of strategies you would employ under logical security measures, these include installation of firewalls to secure the network system, the use of antispyware and virus software. You will also need to have alerts which will let you know of possible threats even before unauthorised access has broken through the defence systems. For example if a wrong password has been used, you may want to have an alert for that because that could be a hacker trying to gain access and you can stop them even before they have gone far.
It can never be over emphasized that all your data on the server needs to be backed up. The backups though should not be stored on the same servers because this data will be needed in case something inevitable happens to the original servers. You may need to higher separate backup servers in a different location from the originals or have portable storage for backed up data. In case of a fire or virus attack, the servers can be shut down but there will still be access to the data through the backups.
This is necessary if the data may be in flight through public networks. Encrypting data that is on the move will help lower the threat of third party access to the data. There are a number of options for this measure so you will need to study which is best.
These are just a few of the measures you can take to ensure safety of the data on your server. Depending on your situation you can incorporate more. Just note that one strategy is not enough, you need to employ a number of them depending on the foreseen threats.