SLAs and Web Hosting


What are Service Level Agreements (SLA) and how are they relevant in web hosting?

In its broadest sense, an SLA is contract between the provider and the user that specifies the level of service that is expected during its term and could either be very general or extremely detailed.

In the context of hosting however, SLAs typically cover server-based resources rather than server performance levels according to Jim Carr in his Network Magazine article Service Level Agreements, and covers three critical areas.

  • Server availability – a minimum of 99.0% uptime (based on a rolling 30-day period) is usually guaranteed and although a 100% uptime is every host’s goal, a 99.5-99.9% is more realistic.
  • Server administration – this includes the host’s management responsibilities, acceptable response times for the restoration of failed servers, metrics for data backup performance, etc.
  • Data backup & storage media handling – details the percentage and frequency of scheduled data backups that will be conducted (99% planned backups should be completed according to the ASP Industry Consortium), as well as overall disaster recovery plan testing.

It could also cover technical support, content issues as well as billing questions.

SLAs have two basic functions according to Norbert Turek in his article A Safety Net for Your Website.

  • `To serve as a basis for discussing available service and their relative costs, planned responses to emergencies, and how unexpected problems are handled; and
  • As a reference for determining if a vendor has met its promises, and, if not, what penalties are due.’

From the host’s point of view, SLAs are important because they offer legal protection and they serve as a measure of their own performance to help then improve their service over time.

Some suggestions for hosts when writing their SLA:

  • set out your clients’ needs and your goals
  • establish a baseline for your service
  • detail what you’re offering and at what price
  • get a lawyer to help your write the contract – include liability provisions, the minimum and maximum levels of performance, contract duration etc.

On the other hand, SLAs are important for you, as consumers, because it tells you what services you’ll be paying for and what rights you do and don’t have.

Sounds good right? But then when you shop around, you might notice that it’s awfully hard to find the SLA of some hosts on their sites, and if you do, they’re usually written in very small texts or are only available on the order form. Why is that the case?

Well, there are three possible explanations for this according to Lars Jensen in his HostByte article Do you know what your hosting SLA is? Either the host

  • doesn’t want to confuse potential customers, or
  • don’t want to scare them off, and
  • they hide it because it reveals too much about their company and what customers are ‘actually’ purchasing.

Jensen thus advises customers to simply move on and look for another host if they can’t find the SLA on the company’s web site. He also cautions that hosts can always change their SLA terms so before you become their customer, it’s important to find out if you’ll be notified of such changes in advance and how long before they take effect.

He suggested some provisions to look for in your SLA:

  • money back guarantee (usually within the first 30 days)
  • uptime guarantee (how it is calculated; do you need to show proof of downtimes before they give refunds?)
  • terms of their refunds/credits for downtime (number of hours; should the hours of downtime be consecutive?)
  • what files are permitted
  • bandwidth and disk space quota
  • domain names
  • miscellaneous (server resources, background running programs, mass mailing and other technical area)

So why should you take time out to read your SLA?’s Dan Lemnaru has some ideas, in his article Why take time to read the Terms of Service?

The following WebHostingTalk threads also offers some added information on the subject: