Discussion
Managing High Available Applications
Hi Team
In this course we learnt "Pega qualifies a server as High Availability if it is available for 99.99% of the time. This means that the system should be down for a maximum of 53 minutes over a year. What does the 53 minutes include? This includes any unplanned outages due to a system crash and all planned outages for upgrading the system."
The shared storage in the below image store the rules and data for different vm's/physical machines? or it is the database. If database, lets take an example we have a Hotfix from Pega support where we need might need to bring DB down (specifically).
Do we really need to bring the DB down (incase suggested in a hotfix)/ or do we need to switch to a failover DB?
In this scenario my application will go down for sometime, if this happens sometimes in a year, the system will not be highly availble enterprise application. Please correct me if my understanding is not correct.
Hi,
As you hinted the shared storage can be a database or shared file storage. Indeed when planning for high availability we need to take many components into account. As an example we could think about:
All of these components have a failure rate where some are wel known (i.e. hardware) and have taken measurements to minimize downtime (hot swappable hard ware components, clusters, distributed databases etc.) At Pega we can only take responcibility for our own components. This means even if Pega have created components where we can upgrade one node at a time and have users seamless diverted to other systems to minimize downtime the whole systems high availability is dependent on all components. If the shared storage is made in a way it has to be brought down for a hotfix, yes your system might not be available 99.99% of the year.
A Pega hotfix involving such canges to your database or file system that you need to restart it is very rare, but if, you are correct.