On 2018年06月28日 09:42, Remi Gauvin wrote: > There seems to be a major design flaw with BTRFS that needs to be better > documented, to avoid massive data loss. > > Tested with Raid 1 on Ubuntu Kernel 4.15 > > The use case being tested was a Virtualbox VDI file created with > NODATACOW attribute, (as is often suggested, due to the painful > performance penalty of COW on these files.) NODATACOW implies NODATASUM. From btrfs(5): --- Enable data copy-on-write for newly created files. Nodatacow implies nodatasum, and disables compression. All files created under nodatacow are also set the NOCOW file attribute (see chattr(1)). --- Although it's talking about the mount option, it also applies to per-inode options. Thanks, Qu > > However, if a device is temporarily dropped (this in case, tested by > disconnecting drives.) and re-connects automatically next boot, BTRFS > does not in any way synchronize the VDI file, or have any means to know > that one of copy is out of date and bad. > > The result of trying to use said VDI file is.... interestingly insane. > Scrub did not do anything to rectify the situation. > >
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