Uptime is the amount of time that a server has stayed up and running. This is usually listed as a percentage, like "99.9% uptime." Uptime is a great measure of how good a Web hosting provider is at keeping their systems up and running. If a hosting provider has a high uptime percentage, then that means that their servers stay up and running and so any site you host with them should stay up and running too. Since Web pages can't keep customers if they are down, uptime is very important.
But There are Problems with Grading a Web Host on Uptime
The biggest problem with grading a host on their uptime is that you generally have no way to independently verify it. If the host says they have 99.9% uptime, you have to take them at their word.
But there's more to it. Uptime is almost always defined as a percentage of time. But a percentage of what amount of time? If JoeBlos Web Hosting has a 99% uptime, that means they have a 1% downtime. Over the course of a week, that would be 1 hour, 40 minutes, and 48 seconds that their server is down. Averaged over a year, that would mean that your server would be down as much as 87.36 hours per year or over 3 days. Three days doesn't sound like all that much, until you're not making any sales from the website and are receiving calls from the VP (or worse yet, the CEO). And the frantic calls usually start after 3 hours, not 3 days.
Uptime percentages are misleading. As I pointed out above, 99% uptime sounds great, but it could mean a 3 day outage every year. Here are some mathematical explanations of uptimes:
- 98% uptime = 28.8 minutes/day or 3.4 hours/week or 14.4 hours/month or 7.3 days/year
- 99% uptime = 14.4 minutes/day or 1.7 hours/week or 7.2 hours/month or 3.65 days/year
- 99.5% uptime = 7.2 minutes/day or 0.84 hours/week or 3.6 hours/month or 1.83 days/year
- 99.9% uptime = 1.44 minutes/day or 0.17 hours/week or 0.72 hours/month or 8.8 hours/year
Another way to think about uptime is in how much it will cost you when the server does go down. And all servers go down periodically. If your website brings in $1000 per month, then a host with 98% uptime could lower your profits by $20 every month or as much as $240 per year. And that's just in lost sales. If your customers or search engines start thinking your site is unreliable, they'll stop coming back, and that $1000 per month will start dropping.
When you're choosing your Web hosting provider, look at their uptime guarantees, I recommend only going with a company that offers a guaranteed uptime of 99.5% or higher. Most offer at least 99% uptime guaranteed.
But Uptime Guarantees Can be Misleading Too
Uptime guarantees are not usually what you might think they are. Unless your hosting agreement is very different from every other hosting agreement I've ever seen, the uptime guarantee works something like this:
We guarantee that if your website goes down for more than 3.6 hours per month in unscheduled outages, we will refund the cost of the hosting for the amount of time you reported and they verified your site was down.
Let's break that down:
- How long was the downtime? - We already know that 3.6 hours per month is 99% uptime. So any amount of time that your site is down below that amount of time is within the 1% outage rate that they guarantee. In other words, if your site goes down for 3.5 hours in a month, that's too bad.
- Unscheduled outages - Your hosting service may call it something else, but what this means is that if they let you know that they are going to be performing a server upgrade next weekend, and your site will be down for 72 hours, this is not covered in their uptime guarantee. Most hosts don't take their sites down for more than 4 hours at a time, but problems can happen, and depending upon your hosting agreement, even longer than anticipated maintenance outages will not kick in the uptime guarantee.
- Refunding the cost of hosting - this is the important part. If your website earns $1000 a month in sales and is down for 4 hours, you've lost $5.56. Most hosting packages cost around $10-20 per month. So they will refund you between 6 and 12 cents.
- You reporting the outage - many uptime guarantees only refund you your money if you report the outage. And then they only refund you for the amount of time that you noticed your site was down. This is fine if you have monitoring systems to let you know the minute your site goes down and comes back up again. But most of us don't, so you won't be reimbursed for the full outage if you don't know how long it really was.
Other Uptime Issues
Software vs. Hardware
Uptime is a reflection of how long the machine that is running your website stays up and running. But that machine can be up and working and your website down. If you aren't maintaining the Web server software (and other software like PHP and databases) for your site, you should make sure that your hosting agreement includes guarantees for the software running time as well as hardware uptime.
Who Caused the Problem
If you did something to your website that broke it, that will almost never be covered by an uptime guarantee.
If you've determined that your website went down through no fault of your own, and it was the hardware crashing rather than software (or software was covered in your agreement), it can be difficult to get your reimbursement. Most hosting providers have a lot of hoops they want you to jump through to claim the reimbursement. They are probably hoping that you will decide that the amount of effort involved is not worth the 12 cents you'll receive.
Uptime is Still Important
Don't be mistaken, having a hosting provider that guarantees uptime is much better than one that doesn't. But don't assume that if a provider guarantees 99.9999999999999999999999% uptime that your site will never go down. What it more likely means is that if your site does go down you'll be reimbursed for the cost of the hosting during the down time.