Linux · btrfs

You want to store a large database file or a VM disk image on btrfs without the usual COW fragmentation penalty. What do you set, and what is the catch on an existing non-empty file?

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When you modify a file on btrfs, what happens to the original disk blocks holding that data?

A colleague assumes btrfs is the universally adopted next-gen Linux filesystem. Where does the vendor picture actually diverge?

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In btrfs terms, what is a subvolume, and how is it different from just making a directory?

When you list subvolumes, the top-level root subvolume never appears in the output. What ID does it always carry, and why does that matter?

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