Chris Murphy posted on Thu, 30 Jan 2014 20:00:39 -0700 as excerpted: > Another question for Johann is what exact balance command was to go back > to single? Was there -dconvert and -mconvert? Both are required to go > from raid1/raid to single/DUP or single/single, and actually get rid of > the 2nd device. And looking at the man page, I'm not sure how we do that > conversion and specify which multiple device we're dropping: > > [filesystem] balance start [options] <path> > > With a missing device, presumably this is obvious, but… Of course the normal no-missing-device usage of a balance converting back to single would be one of: 1) Multi-device raidN converting back to single with all devices present, presumably either to get more space (from raid1/5/6/10), or to get back /some/ device-loss tolerance when converting back from raid0 (presumably a data-only conversion in that case, with metadata kept as the default multi-device raid1). 2) Single-device, converting metadata-only to single from dup, either for space reasons, or because the physical device is SSD (in which case single-device metadata default is used due to some devices doing hardware/ firmware dedup with the effect of dup metadata on such a device thus not entirely predictable anyway), possibly an ssd that does deduping in hardware, so dup mode's not particularly useful and is somewhat unpredictable in any case. IOW, just because it's a conversion to single mode doesn't mean we're dropping a device, and a rebalance to single mode wasn't in fact designed to drop a device (that's what device delete is for), so it doesn't really need a way to specify a device to drop. If one is missing, a rebalance will obviously rebalance to existing devices, that's obvious, but otherwise, balance isn't the command for that, device delete is. But your question to Johann remains valid, since we don't know for sure that he was doing the "correct" full balance -dconvert -mconvert, and so far I've simply assumed he was. -- Duncan - List replies preferred. No HTML msgs. "Every nonfree program has a lord, a master -- and if you use the program, he is your master." Richard Stallman -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
