Just wrote a long post explaining all about tiering in bcachefs: https://www.patreon.com/posts/all-about-6751413 Also, tiering should now be working! I'd appreciate help testing it. Notes: Chris Halse Rogers (RAOF in the #bcache IRC channel) has been testing it. He has been seeing an intermittent deadlock while copying large amounts of data, which may or may not be tiering related: if anyone else hits it, I'd really appreciate if you could grab backtraces. Do a "echo t > /proc/sysrq-trigger" and then grab the full dmesg log - that should be enough to figure out what the deadlock is. I haven't gotten to device add/remove yet, don't try it - you'll need to create a new filesystem: bcache format --tier 0 <SSD> --tier 1 <HDD> Also, if you've already been playing with tiering, I highly recommend you create a new filesystem. One of the bugs was an issue with which pointers are considered dirty - in an extent with a tier 0 pointer and a tier 1 pointer, the tier 0 pointer was being considered dirty instead of the tier 1 pointer (with predictably bad consequences; tier 0 would fill up because the tiering thread wasn't actually making anything on tier 0 clean). On a fixed kernel, as extents are migrated it'll end up fixing which pointers are considered dirty which may or may not trigger assertions as which pointers are considered dirty changes. -- To unsubscribe from this list: send the line "unsubscribe linux-bcache" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
