question Re: High Availability in Support Questions

High Availability

bcr6 — Tue, 07 Feb 2017 17:28:06 GMT

what if both active and standby namenodes failed?

Re: High Availability

pvillard — Tue, 07 Feb 2017 17:34:15 GMT

If both NameNodes are down, your HDFS filesystem cannot be used by the platform and there is not much you can do since most of the applications rely on HDFS.

Re: High Availability

bcr6 — Tue, 07 Feb 2017 18:42:23 GMT

Thanks Villard.

Let ,I am on standby name node , it also failed . the resource very critical. I am not able to solve the active namenode, how I can handle this , and how much time taken to reconnect this . let it be a big billion day .I am not backup the namenode. ?

Re: High Availability

pvillard — Tue, 07 Feb 2017 18:44:20 GMT

Please provide the logs of both name nodes to understand what is going on.

Re: High Availability

bcr6 — Wed, 08 Feb 2017 13:01:26 GMT

Thanks Pierre.

I just want to know how to handle, if this question occurs ?

Re: High Availability

rajsyrus — Wed, 08 Feb 2017 15:39:57 GMT

@Rayadu

It depends on what type of failure, if it is a physical failure, then very hard to recover, if it is service failure, based on the logs we can resolve the issue.

Re: High Availability

pvillard — Wed, 08 Feb 2017 15:47:29 GMT

Well, hard to tell... but to have two name nodes should prevent you to get into this situation. I believe that we will support more than 2 name nodes in next versions of HDP.

Also, just to clarify, if one of your name node fails, the other one will automatically become the active name node, you don't have anything to handle regarding the handover. But as soon as a name node fails, it is recommended to take care of it by looking at the logs and fixing the root cause.

Re: High Availability

bcr6 — Wed, 08 Feb 2017 21:19:56 GMT

Thanks Rajendra,

This question asks in an interview, and he gave an example, like let it be a Big Billion day, and the server crashed due to overload of lot of users then I connected to standby, but it also crashed. how to handle this situation?