How do we avoid app impact when replacing expired SSD LUNs?

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debasis.tcs_69445 asked Sep 27, '21 Erick Ramirez edited Oct 6, '21

How do we avoid app impact when replacing expired SSD LUNs?

Hi Experts

We are using Cassandra open source 3.11.3-E000 version.

Our old SSD Lun would be expired and We need to migrate data to new SSD Lun. In that process our data directory mount point name would not change, we would just copy data from old Lun to new lun. We have 2 data centers one is Active and one is Inactive in terms of traffic.

So I would like to know if following steps would work fine for this data migration?

1. Stop application pointing inactive site Cassandra

2.Stop one of the node of C*

3.Infra will perform new LUN migration and copy data.

4. Start the C* in that node

5. Check nodetool status.

6.Perform them in rolling fashion for all othe nodes.

7.Start application in Inactive site.

In that whole exercise our application would still run in active datacenter Cassandra site. Let me know if that is good way to avoid any impact on active site?

Thanks in advance.

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Answer 1 · 2021-10-06T10:30:11Z

Erick Ramirez answered Oct 6, '21

In theory if your cluster is sized appropriately and the driver is configured correctly, there shouldn't be a need to re-point the application from one DC to the other because your application should be able to tolerate an outage to a single node in the cluster.

In any case, your approach should work. Just make sure that after you start Cassandra in step 4 that you watch the startup sequence and tail the logs. This is the quickest way of catching any issues with the node coming up. Running nodetool status is insufficient for verifying the status of the node. Cheers!

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