What happens in background while increasing compute resources (CPU, RAM) for EC2 instance?

Question

Hello,

need to help.
The case is:
1. Application is running on EC2 instance (r6a.xlarge) with 3TB EBS backed volumes (gp3, 3,000 IOPS, 125Mb/s throughput).
2. Operation system is Linux (RedHat 9).
3. Application is performing backup/restore actions with user data.
4. Due to a high load it was decided to vertically scale instance to r6a.2xlarge.
5. Application generated following error 'I/O error, Primary Chunk '/app_dir/DISKS/DATA01/app_name/rootdbs' -- Offline (sanity)' after resizing operation (instance restart). It is not possible to continue for app to run properly - needed to restore data.

What happens in background during EC2 instance resizing?
Is it the same instance app was running on after change of instance type?
Are the disks unmounted and then mounted back?
 
Thanks

Praveen Kumar K · Accepted Answer

Hello,

During an EC2 instance resize, you have to stop and start the instance. EC2 will start the instance from another underlying hardware, so the EBS volumes will be unmounted from the old hardware and mounted on the new hardware with the new instance type.

Since EBS is persistent storage, if you moved or copied any data into EBS, it will persist.

[+] https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/how-ec2-instance-stop-start-works.html#:~:text=In%20most%20cases%2C%20the%20instance%20is%20migrated%20to%20a%20new%20underlying%20host%20computer%20(though%20in%20some%20cases%2C%20such%20as%20when%20an%20instance%20is%20allocated%20to%20a%20host%20in%20a%20Dedicated%20Host%20configuration%2C%20it%20remains%20on%20the%20current%20host).

User-2019204 · Answer

Thank you very much Praveen!

What happens in background while increasing compute resources (CPU, RAM) for EC2 instance?

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