For additional guidance, check out our community articles detailing the process of migrating from your current platform to Carbonio CE.
For enterprise-level requirements and advanced features, consider checking out Zextras Carbonio – the all-in-one private digital workplace designed for digital sovereignty trusted by the public sector, telcos, and regulated industries.
Zextras transforms your Zimbra infrastructure into a high availability system. It means your servers never go down from the user’s point of view. There are different ways to achieve this, such as having a complete replica of your infrastructure; this doesn’t work for you simply because it’s costly. Zextras, on the other hand, overcome every drawback of simple traditional approaches by introducing new methods and concepts to make Zimbra an extremely efficient HA system.
What Is High Availability
High availability (HA) is an essential characteristic of a system that guarantees a specific availability level for a certain period. For example, an enterprise might need a system availability or uptime of at least 99.99% in a year. HA systems are the only way to guarantee a desirable level of availability.
Availability refers to the ability of the user to obtain service by accessing the system. Regardless of the reason, if a user cannot access the system, it is considered unavailable from its point of view. This period of unavailability is referred to as downtime. Availability is usually expressed in terms of the number of nines present in the availability percentage, as the following table:
| Availability % | Downtime per year | Number of 9s |
|---|---|---|
| 99% | 3.65 days | two |
| 99.9% | 8.77 hours | three |
| 99.99% | 52.60 minutes | four |
| 99.999% | 5.26 minutes | five |
The Importance of High Availability
In August 2013, Amazon ended up losing over $990,000 in a 15 minutes downtime. These figures are huge even for a large company like Amazon.
In recent years, IT’s progressive increase has made HA systems popular in industries that their income directly relies on their user’s satisfaction and system availability. Hospitals and data centers that require high availability of their systems to perform daily activities also hugely benefit from HA systems.
Who Needs It
The higher performance we gain from high availability is always beneficial. However, it costs too. You must ask yourself.
- Are your services important in running your business?
- Are these potential downtimes damaging for your company?
If your answer to either of the above questions is positive, the decision is much easier.
Zextras Is Not Just A Traditional HA System
Traditionally high availability systems consist of a set of loosely coupled servers with failover capabilities. This is far from being perfect. Zextras has tried to overcome every drawback of simple traditional approaches by introducing new methods and concepts to make Zimbra an extremely efficient HA system. Replication and Heartbeat technologies are two examples that you can learn more about on How Zextras High Availability Works.
How Zextras Achieved It
Although HA is exceptionally advantageous in many industries, implementing a well-designed HA system can be complicated given the vast range of software, hardware, and deployment options. However, a successful effort always starts with determining business requirements and defining our needs. This is precisely what Zextras has done to pursue its HA approach.
Zextras achieved this goal using the application approach, as opposed to hardware and operating system approaches.
Let’s Compare Three Approaches
HA can be done through different approaches based on fail tolerance:
- Hardware (VSAN, clustered hardware) – When several machines write on the same disk.
- Operating system (DRDB + vIP) – Like above, OS writes on different physical disks without.
- Application – This approach is far more intelligent and considers what is happening to the files.
Advantage of Application Approach
The main advantage of the application approach over the other two methods is that it considers what happens to the files. The other two methods don’t care about the essence of the operation affecting the file and continue to replicate it over all the nodes. For example, an admin makes a mistake and physically deletes a file on a mailstore. In both cases, the same operation is replicated over all the other nodes regardless of being a mistake.
- In the hardware approach, when you delete the file from the disk, it is replicated on other instances using the same disk no matter what.
- In the operating system approach, when you delete the file from one physical disk, the OS doesn’t care and does the same operation on the second one as well.
- In the application approach, you know what is supposed to happen to which data and decide which operations should be replicated, which files can be altered, and which accounts should have HA. For example, you know if it’s a log or temp file, or maybe it’s something that the application shouldn’t alter, such as removing one file or encryption at a low level.
Using the application approach was a revolutionary change. This smart nature improves the availability of servers equipped with the Zextras extensively, which is more economical than other methods.
To learn how Zextras HA works please refer to How Zextras High Availability Works where we explain Zextras HA unique features, advantages, and functionalities.