HDD dying or just a bad cable?

[etorix]

Drive Troubleshooting Flowchart

Do You Think You Have A Drive Issue? Use the flowcharts here to help you diagnose your problem. You will have a definitive answer much sooner than asking for help and waiting on a reply, followed by asking questions for more data, running tests, etc. Save yourself some time and learn a little bit in the process of using these flowcharts. These are very simple to follow flowcharts to diagnose drive problems/failures. There is a small bit about ZFS problems as many people will say it must be …

And dont’ forget:

Joes Rules to Asking for Help

Purpose: To assist people posting clear and informative requests for help and to define the absolute minimum information required in order to provide the helper what is needed and to reduce assumptions. EDIT: I have moved the specific areas of interest to separate entries below. Please read Joes Rules before posting anything Drive Failures Drive Speed Tests Network Issues Software Issues Build Advice Joes Rules Be considerate. This rule applies to both the person asking a question a…

Your post provides no information on the hardware, wiring.
And we’re left wondering whether you actually went through “backup-destroy-restore” or merely expanded the initial raidz1 instead of going for raidz2.