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“The Table of Nines” and High Availability

Having high availability means that your systems and applications are available upon user request or demand. High availability solutions aim to maximize uptime and minimize downtime. The standard of consistent availability has made the global Internet a mechanism for sharing information by extending the reach of database applications throughout the world. Our businesses today require data management solutions that are always available since we have become accustomed to having access to our data and information on demand, 24-hours a day.

Availability is often measured in the percentage of uptime in one year. It is important to note that uptime and availability are not the same thing. For example, if there is a network failure, a system can be “up” but “not available” to the end users.

The Table of Nines

The High Availability Table of Nines

A common system for grading application/service uptime is using the “Table of Nines.” Service availability is often measure in “nines” and when it comes to Service Level Agreements (SLAs) from your Internet Service Providers (ISPs), they will guarantee what percentage of uptime your business will have based on the service you opt for. Of course, the higher the grade/availability, or the more “nines,” the more you’ll be paying for the service.

 

“One Nine”

If you opt for a SLA from your ISP with a grade of “one nine” then your application/service will be up 90% of the time. This means that your service and applications are guaranteed to be up 328.5 days of the year and you’ll have approximately 36.5 days of downtime. This is one of the cheapest SLAs you can get and is not recommended for businesses that rely on their Internet service connections or business applications to function.

“Two Nines”

If you opt for a SLA with a grade of “two nines” then your applications and services will be available 99% of the time. Your applications should have 361.35 days of uptime per year and will have potential downtime of 3.65 days per year. While this is a big upgrade from the 36.5 days of downtime your business would experience with an SLA with “one nine,” having your applications down for almost four days could have a serious effect on your business.

“Three Nines”

If your availability uptime is “three nines” then your application is available 99.9% of the time. While this sounds like a good grade to get, this means that each week, your application has approximately 10.1 minutes of downtime, 43.2 minutes of downtime per month and 8.76 hours of downtime per year. For a lot of businesses, 8.76 hours of downtime every year is too much.

“Four Nines”

If your application availability is “four nines” then your application is available 99.99% of the times, hence the “four nines.” This is a better grade than “three nines” so the application availability will have less downtime than with the “three nines” grade. An application with a grade of “four nines” will have approximately 1.01 minutes of downtime per week, 4.32 minutes of downtime per month and 52.56 minutes of downtime per year. Knowing that your applications will most likely have less than an hour of downtime every year is a great comfort for network managers.

“Five Nines”

One of the best grades in the Table of Nines is “five nines,” or an application uptime of 99.999%. This means that your application should only be down .001% of the time. Breaking that down, this means that your application should only be down approximately 6.05 seconds per week, 25.9 seconds per month and should only have 5.26 minutes of downtime per year. For businesses who need to be available all the time, this is almost as good as it gets.

“Six Nines”

The best and most expensive of all SLAs for service and application uptime would be “six nines” or an uptime 99.9999% of the time. Breaking that down into time, that means that your system and applications shouldn’t be down more than 31.54 seconds every year. That is less than 3 seconds of downtime per month and less than a half-second of downtime per week. For businesses that can’t afford to be unavailable, this is the best, most expensive option.

As we’ve seen, there are many different levels of high availability service agreements.  You should choose a high availability service relative to how much time your business can afford to be unavailable without experiencing detrimental consequences. Of course, the numbers we’ve discussed in terms of uptime are not all inclusive. There are many issues that can arise that may result in your system being “up” but “not available” to your end users. It is important that you work with a high availability service provider that has years of experience in providing highly available networks and can give you the uptime you require.

Our cloud-based-routing service, VXNet, can provide high availability beyond circuit failures and protect your business' services from natural disasters. VXNet has the ability to move your individual VXNet-enabled IP addresses to anywhere in the world in case of any natural disasters or network or in office failures or outages. We transparently provide Enterprise-Grade high availability, even over broadband circuits, which typically take days to repair.

With most businesses relying so heavily on the Internet for their everyday operations, nothing is more important to your company's productivity than having high availability and being accessible to your clients, customers and employees. To help determine which level of high availability your business needs, or how many “nines,” contact us today and one of our experienced network engineers will help you implement the best high availability solution for your business! 

 

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