To explain in case someone doesn't know what this means, it's something BTRFS doesn't have (and AFAIK isn't even on the roadmap). It means you could have, say, an SSD and a more reliable HDD RAIDed such that every stripe on the HDD counts as multiple writes; and you might set that system up so that the SSD is read with priority, and the HDD is written in the background, so that - even though you have a slow drive in the RAID, throughput happens at the faster SSD speeds.
The average user probably won't use this much, but there are all sorts of ways this could be leveraged, by companies, self-hosters, smart OS installation scripts, even removable drive mounters, like udiskie.
To explain in case someone doesn't know what this means, it's something BTRFS doesn't have (and AFAIK isn't even on the roadmap). It means you could have, say, an SSD and a more reliable HDD RAIDed such that every stripe on the HDD counts as multiple writes; and you might set that system up so that the SSD is read with priority, and the HDD is written in the background, so that - even though you have a slow drive in the RAID, throughput happens at the faster SSD speeds.
The average user probably won't use this much, but there are all sorts of ways this could be leveraged, by companies, self-hosters, smart OS installation scripts, even removable drive mounters, like udiskie.