We have all heard about Quorum Server many times, Let's take a few minutes to understand what is it and how it works.
To understand the role of quorum server, we have to understand the Active Active DC Scenario.
I'll explain this in short words.
Active Active DC means that data is synchronized in real time between both data centers, data replication mode is synchronous. In other words, data is written to both DCs. So whenever a desaster occuers at one site, there's no loss of data and services continues running without any interruption. In Huawei, it is achived by using a feature called HyperMetro.
HyperMetro allows two DCs to process services simultaneously and back up each other. In the event of a device fault or DC failure, the other functioning DC automatically takes over services. This ensures robust reliability, enhanced service continuity, and higher storage resource usage.
Now, If the link between two data centers breaks down, data cannot be synchronized between the two data centers and only one data center continues providing services. Arbitration is a mechanism which ensures data and service consistency and continuity by automatically switching the services if something goes wrong in any site.
HyperMetro supports two arbitration modes:
Static Priority Mode: Applies to scenarios where no third-place quorum server is deployed.
Quorum Server Mode: Applies to scenarios where third-place quorum servers are deployed.
In Static Priority Mode, if a fault occurs at site A, site B won't take over automatically, you have to manually shift the services to site B. It is not recommended method.
Below is an example of faults in Static priority mode,
In Quorum Server mode, if a fault occurs at site A, quorum server automatically shifts the srrvices to site B so there's no interruption in services. This is a recommended method.
In Quorum Server Mode, you can determine whether the storage systems work properly based on the heartbeats between storage systems in the data center. If the storage array in one data center crashes or the link between two storage arrays is down, the storage array in each data center sends an arbitration request to the quorum server. The storage array that wins the arbitration continues providing services but the storage array that fails in the arbitration stops providing services. The preferred site takes the precedence in an arbitration.
There are different types of faults in quorum server mode, below is an example of fault types and how they are tolerated.
For complete list of faults in quorum server and how they are tolerated, you can see the link below for details.
https://support.huawei.com/enterprise/en/doc/EDOC1000084209/b6f10d32/arbitration-mechanism
Here's video explaning Hypermetro and Quorum Server in details. It is very helpful. Check the link below.
https://www.youtube.com/watch?v=G2K4XPYyrrc
Here's a video explaining how to configure HyperMetro step by step. Check the link below
https://www.youtube.com/watch?v=ofOiz58pbKY&t=128s
Here's a link for HyperMetro feature guide. Check the link below.
https://support.huawei.com/enterprise/en/doc/EDOC1000181497
Hope this helps someone. I collected this information when i was preparing for my HCIE. If you are preparing for HCIE, you'll find this helpful too. Thank You
