The question came through Gmail chat with no subject line.
If you expand an array of drives in Linux, do you need to reformat the array?
It was followed immediately by, "quick question."
The chat is only three messages long. My answer is not in it. The question does not identify the RAID controller, filesystem, volume manager, operating system, or backup plan. Without those details, there is no single safe answer.
Adding a physical drive was only one part of expanding an array. The controller had to recognize it. The storage layer had to include the new capacity. The filesystem then had to grow into that space, assuming the particular setup supported doing so without rebuilding it. A current backup mattered before any of those steps.
Those are the questions I would need to ask before changing anything.
My work at Beatport included Linux systems, storage, networks, and servers. The store depended on music files, previews, customer data, and the systems around them. I knew the kind of problem he was asking about. I still needed the details of his machine.
This copy of the chat stops after "quick question." It does not say what controller he had or what happened to the array.
What remains is a small and very specific technical problem: somebody had a Linux drive array, wanted to expand it, and did not want to erase the data already there.
The next step was not reformatting anything. It was finding out what he was actually running first.