On Tue, 2015-12-29 at 19:06 +0100, David Sterba wrote: > > Both open of course many questions (how to deal with crashes, > > etc.)... > > maybe having a look at how mdadm handles similar problems could be > > worth. > > The crash consistency should remain, other than that we'd have to > enhance the balance filters to process only the unconverted chunks to > continue. What about nodatacow'ed files? I'd expect that in case of a crash during reshaping, these files are (likely) garbage then right? Not particularly desirable... But probably that just goes in the direction of the issues/questions I brought up in the other thread where I've asked the devs for possibilities in terms of checksumming on nodatacowed areas: i.e. stability/integrity of such files For me, speaking with the sysadmin's hat, that was always the main reason not to do reshapes so far, especially when data is quite precious, which at least one typical use case for nodatacow is, namely DBs. So having crash resistance for CoW + nodataCoW during RAID reshape should be desired. Time for a journal in btrfs? O;-) Cheers, Chris.
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